1032-00003 · Client 1032 · Engagement & Administration

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CALDERWOOD & HARKNESS LLP Attorneys at Law

One Liberty Plaza, 42nd Floor New York, NY 10006

Telephone: (212) 555-7400 Facsimile: (212) 555-7401 www.calderwoodharkness.com

January 15, 2026

VIA EMAIL AND INTERNATIONAL COURIER

Halcyon Semiconductor Aktiengesellschaft Maximilianstraße 72 80539 Munich, Germany

Attn: Wilhelm Ostermann

General Counsel (Chefjustitiar)

cc: Katarina Dalmqvist, Chief Financial Officer (Finanzvorstand)

Re: Supplement to Engagement Letter dated January 12, 2026 — Tax Advisory Services in Connection with the Proposed US Initial Public Offering of American Depositary Shares

Matter No.: 1032-00003

Dear Mr. Ostermann:

1. Introduction and Purpose

This Supplement to Engagement Letter (this "Supplement") is entered into by and between Calderwood & Harkness LLP ("Calderwood & Harkness" or the "Firm") and Halcyon Semiconductor Aktiengesellschaft, a stock corporation (Aktiengesellschaft) organized under the laws of the Federal Republic of Germany ("Halcyon" or the "Company"), with reference to the executed Engagement Letter dated January 12, 2026 (the "Engagement Letter"), pursuant to which Calderwood & Harkness agreed to serve as US legal counsel to Halcyon in connection with the proposed transaction described below.

The purpose of this Supplement is to define more precisely the scope of the tax advisory services to be provided by Leonard Cross, Specialist Partner in the Tax Practice Group of Calderwood & Harkness (the "Tax Advisory Services"), in connection with the proposed initial public offering by Halcyon of American Depositary Shares ("ADSs") in the United States (the "Offering" or the "Transaction").

This Supplement forms an integral part of the Engagement Letter and is governed by the same terms and conditions set forth therein, including, without limitation, fee arrangements, confidentiality provisions, limitation of liability, conflict of interest provisions, and dispute resolution mechanisms. In the event of any conflict between this Supplement and the Engagement Letter, the Engagement Letter shall control, except with respect to the specific scope of Tax Advisory Services defined herein.

The Transaction. As more fully described in the Engagement Letter, the Transaction consists of the proposed initial public offering of ADSs of Halcyon in the United States under a Level III American Depositary Receipt ("ADR") program, with registration on Form F-1 under the Securities Act of 1933, as amended (the "Securities Act"), and listing on the Nasdaq Global Select Market under the proposed ticker symbol "HCYN." The Company is targeting gross proceeds from the Offering of approximately $900,000,000 (nine hundred million US dollars). The ADSs will be issued by Meridian Trust Company, N.A. ("Meridian Trust"), acting as depositary bank, against the deposit of ordinary shares (Stammaktien) of Halcyon, with a ratio of one (1) ADS representing two (2) ordinary shares of Halcyon (the "ADS Ratio"). The ADSs will be evidenced by American Depositary Receipts issued pursuant to a Deposit Agreement to be entered into among Halcyon, Meridian Trust, and the holders and beneficial owners of ADSs from time to time.

2. Tax Advisory Team

Lead Tax Advisor. The Tax Advisory Services described in this Supplement will be led by Leonard Cross, Specialist Partner in the Tax Practice Group of Calderwood & Harkness ("Mr. Cross"). Mr. Cross's current billing rate is $1,900 per hour, as set forth in the Engagement Letter. Mr. Cross brings extensive experience in international tax matters arising in the context of cross-border capital markets transactions, including US initial public offerings by foreign private issuers, and has advised on numerous Level III ADR program launches.

Coordination with Capital Markets Team. Mr. Cross will coordinate the Tax Advisory Services in close collaboration with the Firm's Capital Markets team for this engagement, which is led by Vivienne St. Claire, Partner, Capital Markets (the "Responsible Partner" for the engagement), and Robert Adeyemi, Partner, Capital Markets (the "Billing Partner" for the engagement). All material tax deliverables, including the prospectus taxation section and the tax opinion for filing with the Registration Statement, will be reviewed by both Mr. Cross and Ms. St. Claire prior to delivery to the Company or inclusion in any publicly filed document.

Additional Team Members. Additional tax associates or of-counsel attorneys from the Firm's Tax Practice Group may be assigned to assist Mr. Cross with the Tax Advisory Services as the needs of the engagement require. The Company will receive prior notice of any such assignments, including the identity and billing rate of any additional team member. All such personnel will be subject to the billing rates set forth in the Engagement Letter, or as otherwise communicated to the Company in writing.

Coordination with German Counsel. The Company has separately retained Bähr Stein Rechtsanwälte Partnerschaftsgesellschaft mbB ("Bähr Stein"), Munich, as its German legal counsel in connection with the Offering. The relevant Bähr Stein team members for tax-related matters are Dr. Christoph Maurelban, Partner, Capital Markets, and Johanna Weiß, Senior Associate. Mr. Cross will work in tandem with Bähr Stein on all cross-border tax analysis and, in particular, on the integration of the German tax considerations section of the prospectus with the US federal income tax considerations section. For the avoidance of doubt, all German domestic tax law advice remains the sole responsibility of Bähr Stein; the Firm does not provide advice on German tax law.

3. Scope of Tax Advisory Services

The Tax Advisory Services to be provided by Mr. Cross and the Firm's Tax Practice Group in connection with the Offering shall encompass the workstreams described in Sections 3.1 through 3.6 below. The scope described herein is intended to be comprehensive with respect to the anticipated US federal income tax issues arising in connection with the Offering; however, if additional US federal income tax issues are identified during the course of the engagement, the parties may agree in writing to expand the scope of this Supplement accordingly.

3.1 Passive Foreign Investment Company (PFIC) Analysis

Mr. Cross will conduct a comprehensive analysis of Halcyon's status as a "passive foreign investment company" ("PFIC") within the meaning of Sections 1291 through 1298 of the Internal Revenue Code of 1986, as amended (the "Code"). The PFIC analysis is a critical component of the US federal income tax disclosure in the prospectus, as PFIC status would have significant adverse US federal income tax consequences for US holders of ADSs. The PFIC analysis will encompass the following:

(a) Fiscal Years Covered. The analysis will cover Halcyon's fiscal years ended December 31, 2023 ("FY2023"), December 31, 2024 ("FY2024"), and December 31, 2025 ("FY2025", unaudited), with reference to such financial data as may be provided by the Company and its auditors.

(b) Income Test. Application of the income test set forth in Section 1297(a)(1) of the Code, which requires a determination of whether 75% or more of Halcyon's gross income for the taxable year constitutes "passive income" within the meaning of Section 1297(b) of the Code. For this purpose, passive income generally includes dividends, interest, royalties, rents, annuities, and net gains from the sale of property giving rise to such income, subject to certain exceptions. Mr. Cross will analyze the character of each significant category of Halcyon's gross income for each of the three fiscal years under review, with particular attention to income from licensing of semiconductor intellectual property, intercompany royalty arrangements, and investment returns.

(c) Asset Test. Application of the asset test set forth in Section 1297(a)(2) of the Code, which requires a determination of whether the average percentage of assets held by Halcyon during the taxable year that produce passive income or are held for the production of passive income is 50% or more of the total assets of Halcyon. For a publicly traded foreign corporation, the asset test is generally applied on a fair market value basis. Mr. Cross will analyze the composition of Halcyon's asset base, including cash and cash equivalents, working capital, intellectual property, and operating assets, for each of the three fiscal years under review.

(d) Active Business Exception. Preliminary analysis conducted during the engagement scoping process indicates that less than 25% of Halcyon's gross income is passive in character and less than 50% of Halcyon's assets produce or are held for the production of passive income, such that Halcyon is not expected to be classified as a PFIC for any of the fiscal years under review. The PFIC analysis will include a detailed evaluation of this preliminary conclusion, including sensitivity analyses where appropriate, and consideration of any facts or circumstances that might alter the conclusion in future taxable years.

(e) Look-Through Rules for Subsidiaries. Under Section 1297(c) of the Code, in determining the PFIC status of a tested foreign corporation that owns (directly or indirectly) at least 25% by value of the stock of another corporation, the tested foreign corporation is treated as if it held its proportionate share of the assets of the subsidiary corporation and received directly its proportionate share of the income of the subsidiary corporation. Mr. Cross will apply these look-through rules with respect to each of the following subsidiaries of Halcyon:

(i) Halcyon Semiconductor USA Inc. (Delaware corporation);

(ii) Halcyon Power Solutions GmbH (German limited liability company);

(iii) Halcyon Asia Pacific Pte. Ltd. (Singapore private limited company);

(iv) Halcyon Shanghai Semiconductor Co., Ltd. (People's Republic of China limited liability company); and

(v) Halcyon Automotive Components s.r.o. (Czech Republic limited liability company).

(f) Internal PFIC Memorandum. Mr. Cross will prepare a detailed internal memorandum documenting the PFIC analysis and conclusions for each of FY2023, FY2024, and FY2025, together with supporting calculations, assumptions, and data sources. This memorandum is intended for the Company's internal records and for reference by the working group, and is not intended for distribution to investors or inclusion in the Registration Statement.

(g) Future Year PFIC Implications. The PFIC analysis section of the prospectus will include a discussion of the implications for US holders of ADSs in the event that PFIC status were to apply in any future taxable year, including a description of the excess distribution regime under Section 1291 of the Code, the availability and consequences of a qualified electing fund ("QEF") election under Section 1295 of the Code, and the availability and consequences of a mark-to-market election under Section 1296 of the Code.

3.2 US Federal Income Tax Opinion for Prospectus

Mr. Cross will prepare a tax opinion (the "Tax Opinion") regarding the material US federal income tax consequences of the acquisition, ownership, and disposition of ADSs by US holders (as defined in the prospectus). The Tax Opinion will be prepared in accordance with the standards and requirements applicable to tax opinions filed in connection with registered offerings under the Securities Act and will address the following key topics:

(a) Classification of ADSs. The Tax Opinion will address the classification of the ADSs as equity for US federal income tax purposes, including the treatment of holders of ADSs as the owners of the underlying ordinary shares of Halcyon for US federal income tax purposes, consistent with established IRS guidance and case law regarding the tax treatment of American Depositary Shares.

(b) Distributions on ADSs. The Tax Opinion will address the US federal income tax treatment of distributions made on the ADSs, including the characterization of such distributions as dividends (to the extent paid out of the Company's current or accumulated earnings and profits as determined for US federal income tax purposes), return of capital (to the extent in excess of earnings and profits), or capital gain. The Tax Opinion will also address the translation of euro-denominated distributions into US dollars for tax purposes and any foreign currency gain or loss that may arise as a result of such translation.

(c) Qualified Dividend Income. The Tax Opinion will address the eligibility of dividends paid on the ADSs for the reduced rates of tax applicable to "qualified dividend income" under Section 1(h)(11) of the Code for individual US holders and certain other non-corporate US holders. This analysis will take into account, among other factors, the requirement that Halcyon not be a PFIC for the taxable year in which the dividend is paid or the preceding taxable year, and the requirement that certain holding period conditions be satisfied.

(d) PFIC Conclusions. The Tax Opinion will include a discussion of the Company's PFIC status, cross-referencing the PFIC analysis described in Section 3.1 above, and will describe the consequences to US holders if the Company were to be classified as a PFIC in any future taxable year.

(e) Disposition of ADSs. The Tax Opinion will address the US federal income tax consequences of a sale, exchange, or other taxable disposition of ADSs by a US holder, including the recognition of capital gain or loss, the determination of the holding period for purposes of distinguishing between long-term and short-term capital gain or loss, and the determination of the US holder's tax basis in the ADSs.

(f) Foreign Currency Gain or Loss. The Tax Opinion will address any foreign currency gain or loss that may be recognized by a US holder on the receipt of euro-denominated distributions on the ADSs, including the application of Section 988 of the Code to such transactions.

(g) Information Reporting and Backup Withholding. The Tax Opinion will address the information reporting obligations and backup withholding requirements under Section 3406 of the Code that may apply to distributions on, and proceeds from the sale or other disposition of, ADSs held by US holders.

(h) FATCA. The Tax Opinion will address the potential application of the Foreign Account Tax Compliance Act ("FATCA"), as codified in Sections 1471 through 1474 of the Code, and the Treasury Regulations and IRS guidance thereunder, to payments made with respect to the ADSs. The analysis will consider the applicability of the US-Germany intergovernmental agreement (the "IGA") implementing FATCA in Germany.

(i) Filing and Inclusion in Prospectus. The Tax Opinion, or a summary thereof, is intended to be included in the "Taxation" section of the prospectus forming part of the Registration Statement on Form F-1. To the extent required by applicable SEC rules and guidance, including Item 601(b)(8) of Regulation S-K, the Tax Opinion will also be filed as an exhibit to the Registration Statement.

(j) Coordination with German Tax Section. Mr. Cross will coordinate with Bähr Stein Rechtsanwälte with respect to the German tax considerations section of the prospectus to ensure consistency between the US and German tax disclosure. Mr. Cross will review and provide comments on the German tax section drafted by Bähr Stein and will work with Bähr Stein to integrate the two sections into a cohesive "Taxation" chapter for the prospectus.

3.3 US/German Tax Treaty Analysis

Mr. Cross will conduct a detailed analysis of the Convention Between the United States of America and the Federal Republic of Germany for the Avoidance of Double Taxation and the Prevention of Fiscal Evasion with Respect to Taxes on Income and Capital and to Certain Other Taxes, signed on August 29, 1989, as amended by the Protocol signed on June 1, 2006 (the "Treaty"), as it applies to the Offering and to the ownership of ADSs by US holders. The Treaty analysis will address the following matters:

(a) Treaty Article 10 — Dividends. A detailed analysis of Article 10 of the Treaty, which governs the taxation of dividends paid by a German company to a US resident. Under current German domestic law, dividends paid by a German corporation are subject to German withholding tax at a statutory rate of 26.375%, comprising the 25% capital gains withholding tax (Kapitalertragsteuer) and the 5.5% solidarity surcharge (Solidaritätszuschlag) thereon. Under Article 10(2)(b) of the Treaty, the rate of German withholding tax on dividends paid to a qualifying US resident is reduced to 15% (or, in certain cases, 5% for corporate shareholders holding at least 10% of the voting stock of the paying company). Mr. Cross will analyze the conditions under which US holders of ADSs will be eligible for the reduced treaty rate.

(b) Limitation on Benefits. The Treaty contains a comprehensive Limitation on Benefits ("LOB") article (Article 28), which imposes requirements on US residents seeking to claim treaty benefits. Mr. Cross will analyze the LOB provisions as applied to various categories of US holders, including individual US holders, US corporations, US partnerships, US pension funds (including 401(k) plans and individual retirement accounts), and US tax-exempt organizations described in Section 501(c)(3) of the Code. The analysis will identify any categories of US holders that may not qualify for treaty benefits under the LOB article and will discuss the implications for such holders.

(c) US Foreign Tax Credit Analysis. Mr. Cross will analyze the creditability of German withholding taxes paid by US holders of ADSs against their US federal income tax liability, including the application of Section 901 of the Code (which allows a credit for income taxes paid or accrued to a foreign country) and Section 904 of the Code (which limits the foreign tax credit to the US tax attributable to foreign source income). The analysis will address the appropriate separate limitation basket classification for dividends received on the ADSs, including whether such dividends constitute "passive category income" or "general category income" for purposes of Section 904(d) of the Code.

(d) ADS Structure Considerations. The analysis will address potential issues arising from the ADS structure — specifically, the fact that the depositary (Meridian Trust) holds the underlying ordinary shares on behalf of ADS holders — on the entitlement of US holders to claim treaty benefits with respect to German withholding tax. The analysis will consider whether the interposition of the depositary as a registered holder of the underlying shares creates any impediment to the flow-through of treaty benefits to the beneficial owners of the ADSs.

(e) Internal Treaty Memorandum. Mr. Cross will prepare a detailed internal memorandum summarizing the Treaty analysis and conclusions set forth above. This memorandum is intended for the Company's internal records and for reference by the working group, and is not intended for distribution to investors or inclusion in the Registration Statement.

3.4 Qualified Intermediary (QI) Analysis for Meridian Trust Company, N.A.

Mr. Cross will conduct an analysis of the qualified intermediary ("QI") status and obligations of Meridian Trust Company, N.A. (principal office at 101 Barclay Street, New York, NY 10286; contact: Patricia Novak, Vice President, Depositary Receipts) in connection with the Offering and the ongoing administration of the ADS program. The QI analysis will encompass the following:

(a) QI Status. Analysis of Meridian Trust's status as a Qualified Intermediary under the QI Agreement framework established by Revenue Procedure 2017-15, as amended by subsequent revenue procedures and IRS guidance. Mr. Cross will review Meridian Trust's current QI Agreement with the IRS and confirm that Meridian Trust's QI status is in good standing and covers the types of payments expected to be made in connection with the ADS program.

(b) Withholding Responsibilities. Evaluation of Meridian Trust's primary withholding responsibilities with respect to German Kapitalertragsteuer on dividend distributions paid to ADS holders through the depositary arrangement. The analysis will consider the extent to which Meridian Trust, as depositary and QI, is required to withhold German tax at source or is entitled to apply the reduced treaty rate on behalf of US ADS holders for whom appropriate documentation is on file.

(c) Interaction of German Withholding, QI Framework, and Deposit Agreement. Analysis of the interaction among: (i) German withholding tax procedures applicable to dividends paid by Halcyon on the ordinary shares deposited with the depositary; (ii) the QI framework and Meridian Trust's obligations thereunder; and (iii) the Deposit Agreement (which is expected to be governed by the laws of the State of Delaware) through which ADS holders receive distributions. The analysis will identify any procedural or structural issues that could affect the ability of US ADS holders to receive the benefit of the reduced treaty withholding rate at source, as opposed to being required to file for a refund of excess withholding.

(d) Documentation Requirements. Assessment of the documentation requirements that Meridian Trust must satisfy in order to claim treaty benefits on behalf of US ADS holders, including the collection and maintenance of IRS Forms W-8 and W-9 from ADS holders and DTC participants, and any corresponding German tax documentation.

(e) Coordination with German Counsel. Mr. Cross will coordinate with Bähr Stein Rechtsanwälte regarding the procedures of the German Federal Central Tax Office (Bundeszentralamt für Steuern) for granting treaty relief at source or processing refund claims for excess German withholding tax. This coordination will ensure that the QI analysis is consistent with German procedural requirements.

(f) Internal QI Memorandum. Mr. Cross will prepare a memorandum documenting the QI analysis and recommendations, including any operational steps that Meridian Trust or the Company should take to ensure that the reduced treaty rate is available to eligible US ADS holders. This memorandum is intended for the Company's internal records and for reference by the working group.

3.5 Treaty Benefit Certification Procedures for US ADS Holders

Mr. Cross will analyze the documentation and certification procedures applicable to US ADS holders seeking to claim the reduced 15% treaty withholding rate on dividends paid on the ADSs, and will prepare related recommendations and disclosure materials. This workstream will encompass the following:

(a) IRS Documentation Requirements. Analysis of the IRS documentation requirements for US ADS holders to certify their status as US residents eligible for treaty benefits, including the applicable provisions of Treasury Regulations under Sections 1441 through 1446 of the Code and the QI Agreement.

(b) Forms W-8BEN and W-8BEN-E. Review of the requirements applicable to IRS Form W-8BEN (Certificate of Foreign Status of Beneficial Owner for United States Tax Withholding and Reporting — for individuals) and IRS Form W-8BEN-E (Certificate of Status of Beneficial Owner for United States Tax Withholding and Reporting — for entities), as they apply to US ADS holders claiming treaty benefits under the Treaty. The analysis will distinguish between the documentation required from individual and entity holders and will address any special considerations applicable to particular categories of entity holders (e.g., partnerships, trusts, and pension funds).

(c) Certification Chain. Analysis of the certification chain through which treaty benefit claims flow from the beneficial owner of the ADSs through the relevant intermediaries, including: (i) the ADS holder; (ii) the DTC participant through which the ADS holder holds its position; (iii) Crestfield Transfer Services Inc. (transfer agent and registrar for the ADSs, located at 6201 15th Avenue, Brooklyn, NY 11219; contact: Angela Moretti, Director, Corporate Actions); and (iv) Meridian Trust as depositary. The analysis will identify any breaks or weaknesses in the certification chain that could impede the flow-through of treaty benefits.

(d) Certification Procedures Memorandum. Mr. Cross will prepare a memorandum describing the certification procedures and recommending appropriate disclosure for inclusion in the prospectus (in the "Taxation" section) to inform US ADS holders of the documentation steps required to claim the reduced treaty rate.

(e) Form W-8BEN-E for Halcyon Semiconductor AG. Mr. Cross will draft or review IRS Form W-8BEN-E for Halcyon Semiconductor AG itself, to be used by the Company in connection with its interactions with US withholding agents and financial institutions. The Form W-8BEN-E will include the Company's entity classification for US federal income tax purposes, the Company's FATCA status and applicable FATCA exemption code, and the Company's Legal Entity Identifier ("LEI"): 5299007KBTVZ3XQHGL48. This form will be prepared in accordance with the instructions to Form W-8BEN-E and applicable Treasury Regulations.

3.6 Additional Tax Advisory Matters

In addition to the principal workstreams described in Sections 3.1 through 3.5, Mr. Cross will provide advisory services on the following additional US federal income tax matters arising in connection with the Offering:

(a) Tax-Related Risk Factors. Review of and comment on the tax-related risk factors to be included in the prospectus, including risk factors relating to PFIC status, changes in US or German tax law, and the availability of treaty benefits.

(b) Selling Shareholder Withholding. Advice on the US withholding tax implications, if any, for the selling shareholders participating in the Offering, specifically Rheintal Industrieholding GmbH (a German limited liability company) and Kestrel Capital Partners AG (a Swiss stock corporation). Both selling shareholders are non-US entities, and the analysis will address whether any US withholding tax obligations arise in connection with the sale of ADSs by such entities in the Offering.

(c) Use of Proceeds. Review of any US tax implications arising from the Company's intended use of the net proceeds of the Offering, including the proposed repayment of approximately $100,000,000 of the revolving credit facility tranche, and advice on whether any such use of proceeds gives rise to US federal income tax consequences that should be disclosed in the prospectus.

(d) US Subsidiary Tax Reporting. Advice on any US tax reporting obligations arising from the Company's US subsidiary, Halcyon Semiconductor USA Inc. (a corporation organized under the laws of the State of Delaware; Employer Identification Number: 84-3927561; principal office at 2500 Augustine Drive, Suite 100, Santa Clara, CA 95054), including any information reporting obligations that may be triggered or affected by the Offering.

(e) Transfer Pricing. Advice on any transfer pricing considerations relevant to prospectus disclosure, including the disclosure of material intercompany transactions between Halcyon and its subsidiaries that could give rise to transfer pricing adjustments or disputes with tax authorities, to the extent such matters are material to the US federal income tax analysis.

(f) FIRPTA. Advice on any considerations arising under the Foreign Investment in Real Property Tax Act ("FIRPTA"), as codified in Sections 897 and 1445 of the Code, to the extent applicable to the Company, the ADSs, or the Offering. In particular, Mr. Cross will evaluate whether Halcyon could be classified as a "United States real property holding corporation" within the meaning of Section 897(c)(2) of the Code, and, if so, the implications for US holders of ADSs upon a disposition of their interests.

4. Deliverables

Mr. Cross will prepare and deliver the following work product in connection with the Tax Advisory Services described in this Supplement. All target delivery dates are subject to the overall transaction timeline and may be adjusted by mutual agreement of the parties in consultation with the Capital Markets team:

1. PFIC Analysis Memorandum (Internal). A detailed internal memorandum documenting the PFIC analysis and conclusions for FY2023, FY2024, and FY2025, together with supporting calculations, assumptions, and data sources. Target Delivery Date: Prior to circulation of the first draft of the Registration Statement on Form F-1 (March 9, 2026).

2. US/German Tax Treaty Memorandum (Internal). A detailed internal memorandum summarizing the analysis of the Treaty as applied to the Offering and the ownership of ADSs by US holders, including the LOB analysis, foreign tax credit analysis, and ADS structure considerations. Target Delivery Date: Prior to circulation of the first draft of the Registration Statement on Form F-1 (March 9, 2026).

3. Draft Prospectus Taxation Section (US Federal Income Tax Consequences). A draft of the "US Federal Income Tax Consequences" section of the prospectus, covering all topics described in Section 3.2 of this Supplement. This draft will be prepared for incorporation into the first draft of the Form F-1. Target Delivery Date: To be incorporated in the first draft of the Registration Statement on Form F-1 (March 9, 2026).

4. QI Analysis Memorandum (Internal). A memorandum documenting the analysis of Meridian Trust's QI status, withholding responsibilities, and operational recommendations. Target Delivery Date: By the all-parties drafting session (March 23–24, 2026).

5. Treaty Benefit Certification Procedures Memorandum (Internal). A memorandum describing the documentation and certification procedures applicable to US ADS holders claiming the reduced treaty withholding rate, including recommendations for prospectus disclosure. Target Delivery Date: By the all-parties drafting session (March 23–24, 2026).

6. Draft IRS Form W-8BEN-E for Halcyon Semiconductor AG. A completed or substantially completed draft of IRS Form W-8BEN-E for the Company, including entity classification, FATCA status, and LEI. Target Delivery Date: By the confidential submission date for the Registration Statement (April 14, 2026).

7. Final Tax Opinion for Filing with Registration Statement. The final Tax Opinion for filing as an exhibit to the Registration Statement on Form F-1, addressing the material US federal income tax consequences of the acquisition, ownership, and disposition of ADSs by US holders. Target Delivery Date: Prior to the SEC declaration of effectiveness of the Registration Statement (June 22, 2026).

The foregoing deliverables are also set forth in summary table format in Exhibit A attached hereto.

5. Limitations and Exclusions

The Tax Advisory Services described in this Supplement are subject to the following limitations and exclusions:

(a) Scope of Tax Law Coverage. The Tax Advisory Services are limited to US federal income tax law and the US-Germany income tax treaty (the Treaty). All advice on German domestic tax law, including German withholding tax procedures, German corporate tax, German trade tax (Gewerbesteuer), and German value added tax, is the exclusive responsibility of Bähr Stein Rechtsanwälte. Calderwood & Harkness does not provide tax advice under the laws of Germany.

(b) Other Jurisdictions. Calderwood & Harkness does not provide tax advice under the laws of Switzerland (relevant to the selling shareholder Kestrel Capital Partners AG), the Republic of Singapore (relevant to the subsidiary Halcyon Asia Pacific Pte. Ltd.), the People's Republic of China (relevant to the subsidiary Halcyon Shanghai Semiconductor Co., Ltd.), or the Czech Republic (relevant to the subsidiary Halcyon Automotive Components s.r.o.). If tax advice under the laws of any of these jurisdictions is required, the Company should retain separate local counsel with expertise in the applicable tax law. Calderwood & Harkness will cooperate with any such local counsel as reasonably requested.

(c) State and Local Tax. Unless otherwise specifically agreed in writing, the Tax Advisory Services do not include advice on US state or local income, franchise, or other tax law matters. The Tax Opinion for the prospectus will address only US federal income tax consequences and will include a customary disclaimer regarding state and local tax consequences.

(d) Currency of Legal Authority. All tax opinions, memoranda, and other work product delivered pursuant to this Supplement are based upon the Code, Treasury Regulations promulgated thereunder, IRS rulings and administrative guidance, judicial decisions, and the Treaty, in each case as in effect on the date of issuance. Tax law is subject to change, potentially with retroactive effect, and no assurance can be given that the law will not change in a manner that could alter the conclusions set forth in any opinion or memorandum.

(e) No Assurance of IRS Agreement. No assurance can be given that the Internal Revenue Service ("IRS") will agree with any position or conclusion set forth in any tax opinion or memorandum delivered pursuant to this Supplement, or that a court of competent jurisdiction would sustain any such position or conclusion if challenged. The Tax Opinion is not a guarantee of any particular tax result.

(f) Customary Assumptions and Qualifications. The Tax Opinion for the prospectus will be subject to customary assumptions and qualifications, including, without limitation, assumptions regarding the accuracy and completeness of the representations and information provided by the Company, the enforceability of relevant agreements, and the absence of changes in law after the date of the opinion.

6. Fee Arrangements

All Tax Advisory Services provided pursuant to this Supplement will be billed on an hourly basis at the rates set forth in the Engagement Letter dated January 12, 2026. For the avoidance of doubt:

(a) Leonard Cross Billing Rate. Mr. Cross's current billing rate is $1,900 per hour, as set forth in the Engagement Letter. Time spent by Mr. Cross on the Tax Advisory Services will be recorded and billed in accordance with the Firm's standard timekeeping and billing practices.

(b) Additional Tax Personnel. Any additional tax associates or of-counsel attorneys assigned to the engagement will be billed at their applicable rates as set forth in the Engagement Letter or as otherwise communicated to the Company in writing prior to the commencement of such personnel's work on the engagement.

(c) Inclusion in Total Fee Estimate. The fees for the Tax Advisory Services are included within the estimated total legal fees of $3,200,000 to $3,800,000 set forth in the Engagement Letter. There is no separate retainer or fee estimate for the Tax Advisory Services apart from the overall engagement fee estimate. As noted in the Engagement Letter, the fee estimate is a good-faith projection based on the anticipated scope of the engagement and is not a cap or guarantee.

(d) Application of Retainer. The retainer of $250,000 received by the Firm upon execution of the Engagement Letter applies to all services provided under the Engagement Letter, including the Tax Advisory Services described herein. The retainer will be applied against invoices for services rendered in the ordinary course, as set forth in the Engagement Letter.

7. Coordination with Other Advisors

In connection with the Tax Advisory Services, Mr. Cross will coordinate directly with the following external advisors and Company personnel:

(a) Bähr Stein Rechtsanwälte Partnerschaftsgesellschaft mbB. Dr. Christoph Maurelban, Partner, Capital Markets, and Johanna Weiß, Senior Associate, for German tax law matters and the German tax considerations portion of the prospectus. As described above, Mr. Cross will review and comment on the German tax disclosure prepared by Bähr Stein and will work with Bähr Stein to ensure consistency between the US and German tax sections of the prospectus and to coordinate cross-border tax analysis, including Treaty analysis and German withholding tax procedures.

(b) Blackmere & Whitfield LLP / GmbH WPG (Auditors). Dieter Kaufmann, Wirtschaftsprüfer, Munich office, and Graham Templeton, Partner, New York office. Mr. Cross will coordinate with Blackmere & Whitfield regarding financial data to be used in the PFIC analysis, including gross income breakdowns, asset composition data, and subsidiary financial statements. Mr. Cross will also coordinate with Blackmere & Whitfield regarding any tax-related items to be addressed in the accountants' comfort letter, including the agreement of tax-related numerical data in the prospectus to underlying financial records.

(c) Meridian Trust Company, N.A. Patricia Novak, Vice President, Depositary Receipts. Mr. Cross will coordinate with Meridian Trust regarding QI status documentation, depositary withholding procedures, and the operational mechanics of applying the reduced treaty withholding rate to dividend distributions through the ADS program.

(d) Halcyon Internal Contacts. Katarina Dalmqvist, Chief Financial Officer (Finanzvorstand), and Halcyon's internal tax department. Mr. Cross will coordinate with Ms. Dalmqvist and the Company's tax team for company-specific financial and operational data necessary for the PFIC analysis, Treaty analysis, and withholding analyses, including revenue classification data, intercompany transaction records, asset valuations, subsidiary financial statements, and any prior tax rulings or correspondence with tax authorities relevant to the scope of the Tax Advisory Services.

8. Governing Terms

This Supplement is governed by and subject to all terms, conditions, and provisions of the Engagement Letter dated January 12, 2026, including, without limitation, the provisions relating to:

(a) confidentiality and the protection of privileged communications;

(b) conflicts of interest and the Firm's conflict clearance procedures;

(d) dispute resolution, including any arbitration or mediation provisions;

(e) the governing law and jurisdiction provisions; and

(f) the termination provisions.

In the event of any conflict or inconsistency between this Supplement and the Engagement Letter, the Engagement Letter shall control in all respects, except that this Supplement shall control with respect to the specific scope of Tax Advisory Services to be provided by Mr. Cross and the Firm's Tax Practice Group, including the deliverables and target delivery dates set forth herein.

This Supplement may be amended, modified, or supplemented only by a written instrument signed by an authorized representative of each of Calderwood & Harkness and Halcyon.

9. Counterparts and Acknowledgment

This Supplement may be executed in one or more counterparts (including by means of electronic signatures transmitted by email or electronic signature platform), each of which shall be deemed an original and all of which, taken together, shall constitute one and the same instrument.

We respectfully request that Mr. Ostermann, in his capacity as General Counsel (Chefjustitiar) of Halcyon Semiconductor Aktiengesellschaft, indicate Halcyon's agreement to the terms of this Supplement by executing and returning the countersignature block below. A copy of this Supplement, fully executed by both parties, will be retained in the Firm's files and a copy will be provided to the Company for its records.

We look forward to continuing our work with Halcyon and its advisors on this important transaction. Should you have any questions regarding the scope of the Tax Advisory Services described herein, please do not hesitate to contact Leonard Cross at lcross@calderwoodharkness.com or +1 (212) 555-7438, or Vivienne St. Claire at vstclaire@calderwoodharkness.com or +1 (212) 555-7422.

Very truly yours,

CALDERWOOD & HARKNESS LLP

By: ________

Name: Vivienne St. Claire

Title: Partner, Capital Markets

(Responsible Partner for the Engagement)

By: ________

Name: Leonard Cross

Title: Partner, Tax

(Tax Advisory Lead)

ACKNOWLEDGED AND AGREED

The undersigned, acting on behalf of Halcyon Semiconductor Aktiengesellschaft, hereby acknowledges receipt of this Supplement and agrees to the terms and conditions set forth herein.

HALCYON SEMICONDUCTOR AKTIENGESELLSCHAFT

By: ________

Name: Wilhelm Ostermann

Title: General Counsel (Chefjustitiar)

Date: ________

EXHIBIT A

Summary of Tax Advisory Workstreams and Target Delivery Schedule

The following table summarizes the Tax Advisory Services deliverables described in Section 4 of this Supplement. The "Status" column is provided for the working group's internal tracking purposes and is intentionally left blank at the time of execution of this Supplement.

This Exhibit A is provided for convenience of reference only and is qualified in its entirety by the detailed descriptions of each workstream set forth in Sections 3 and 4 of this Supplement.

No.	Workstream	Description	Lead Attorney	Target Delivery Date	Status
1	PFIC Analysis Memorandum (Internal)	Detailed internal memorandum documenting PFIC analysis and conclusions for FY2023, FY2024, and FY2025, with supporting calculations	Leonard Cross	March 9, 2026 (prior to first draft F-1 circulation)
2	US/German Tax Treaty Memorandum (Internal)	Internal memorandum summarizing Treaty analysis, LOB analysis, foreign tax credit analysis, and ADS structure considerations	Leonard Cross	March 9, 2026 (prior to first draft F-1 circulation)
3	Draft Prospectus Taxation Section (US Federal Income Tax Consequences)	Draft of the "US Federal Income Tax Consequences" section of the prospectus for incorporation in the first draft F-1	Leonard Cross	March 9, 2026 (incorporated in first draft F-1)
4	QI Analysis Memorandum (Internal)	Memorandum documenting analysis of Meridian Trust's QI status, withholding responsibilities, and operational recommendations	Leonard Cross	March 23–24, 2026 (all-parties drafting session)
5	Treaty Benefit Certification Procedures Memorandum (Internal)	Memorandum on documentation and certification procedures for US ADS holders claiming reduced treaty withholding rate; includes prospectus disclosure recommendations	Leonard Cross	March 23–24, 2026 (all-parties drafting session)
6	Draft IRS Form W-8BEN-E for Halcyon Semiconductor AG	Completed or substantially completed draft of IRS Form W-8BEN-E for the Company (entity classification, FATCA status, LEI: 5299007KBTVZ3XQHGL48)	Leonard Cross	April 14, 2026 (confidential submission date)
7	Final Tax Opinion for Filing with Registration Statement	Final Tax Opinion addressing material US federal income tax consequences of acquisition, ownership, and disposition of ADSs by US holders; for filing as exhibit to Form F-1	Leonard Cross	June 22, 2026 (prior to SEC declaration of effectiveness)

CALDERWOOD & HARKNESS LLP Attorneys at Law
One Liberty Plaza, 42nd Floor New York, NY 10006
Telephone: (212) 555-7400 Facsimile: (212) 555-7401 www.calderwoodharkness.com
January 15, 2026
VIA EMAIL AND INTERNATIONAL COURIER
Halcyon Semiconductor Aktiengesellschaft Maximilianstraße 72 80539 Munich, Germany
Attn: Wilhelm Ostermann
General Counsel (Chefjustitiar)
cc: Katarina Dalmqvist, Chief Financial Officer (Finanzvorstand)
Re: Supplement to Engagement Letter dated January 12, 2026 — Tax Advisory Services in Connection with the Proposed US Initial Public Offering of American Depositary Shares
Matter No.: 1032-00003
Dear Mr. Ostermann:
1. Introduction and Purpose
This Supplement to Engagement Letter (this "Supplement") is entered into by and between Calderwood & Harkness LLP ("Calderwood & Harkness" or the "Firm") and Halcyon Semiconductor Aktiengesellschaft, a stock corporation (Aktiengesellschaft) organized under the laws of the Federal Republic of Germany ("Halcyon" or the "Company"), with reference to the executed Engagement Letter dated January 12, 2026 (the "Engagement Letter"), pursuant to which Calderwood & Harkness agreed to serve as US legal counsel to Halcyon in connection with the proposed transaction described below.
The purpose of this Supplement is to define more precisely the scope of the tax advisory services to be provided by Leonard Cross, Specialist Partner in the Tax Practice Group of Calderwood & Harkness (the "Tax Advisory Services"), in connection with the proposed initial public offering by Halcyon of American Depositary Shares ("ADSs") in the United States (the "Offering" or the "Transaction").
This Supplement forms an integral part of the Engagement Letter and is governed by the same terms and conditions set forth therein, including, without limitation, fee arrangements, confidentiality provisions, limitation of liability, conflict of interest provisions, and dispute resolution mechanisms. In the event of any conflict between this Supplement and the Engagement Letter, the Engagement Letter shall control, except with respect to the specific scope of Tax Advisory Services defined herein.
The Transaction. As more fully described in the Engagement Letter, the Transaction consists of the proposed initial public offering of ADSs of Halcyon in the United States under a Level III American Depositary Receipt ("ADR") program, with registration on Form F-1 under the Securities Act of 1933, as amended (the "Securities Act"), and listing on the Nasdaq Global Select Market under the proposed ticker symbol "HCYN." The Company is targeting gross proceeds from the Offering of approximately $900,000,000 (nine hundred million US dollars). The ADSs will be issued by Meridian Trust Company, N.A. ("Meridian Trust"), acting as depositary bank, against the deposit of ordinary shares (Stammaktien) of Halcyon, with a ratio of one (1) ADS representing two (2) ordinary shares of Halcyon (the "ADS Ratio"). The ADSs will be evidenced by American Depositary Receipts issued pursuant to a Deposit Agreement to be entered into among Halcyon, Meridian Trust, and the holders and beneficial owners of ADSs from time to time.
2. Tax Advisory Team
Lead Tax Advisor. The Tax Advisory Services described in this Supplement will be led by Leonard Cross, Specialist Partner in the Tax Practice Group of Calderwood & Harkness ("Mr. Cross"). Mr. Cross's current billing rate is $1,900 per hour, as set forth in the Engagement Letter. Mr. Cross brings extensive experience in international tax matters arising in the context of cross-border capital markets transactions, including US initial public offerings by foreign private issuers, and has advised on numerous Level III ADR program launches.
Coordination with Capital Markets Team. Mr. Cross will coordinate the Tax Advisory Services in close collaboration with the Firm's Capital Markets team for this engagement, which is led by Vivienne St. Claire, Partner, Capital Markets (the "Responsible Partner" for the engagement), and Robert Adeyemi, Partner, Capital Markets (the "Billing Partner" for the engagement). All material tax deliverables, including the prospectus taxation section and the tax opinion for filing with the Registration Statement, will be reviewed by both Mr. Cross and Ms. St. Claire prior to delivery to the Company or inclusion in any publicly filed document.
Additional Team Members. Additional tax associates or of-counsel attorneys from the Firm's Tax Practice Group may be assigned to assist Mr. Cross with the Tax Advisory Services as the needs of the engagement require. The Company will receive prior notice of any such assignments, including the identity and billing rate of any additional team member. All such personnel will be subject to the billing rates set forth in the Engagement Letter, or as otherwise communicated to the Company in writing.
Coordination with German Counsel. The Company has separately retained Bähr Stein Rechtsanwälte Partnerschaftsgesellschaft mbB ("Bähr Stein"), Munich, as its German legal counsel in connection with the Offering. The relevant Bähr Stein team members for tax-related matters are Dr. Christoph Maurelban, Partner, Capital Markets, and Johanna Weiß, Senior Associate. Mr. Cross will work in tandem with Bähr Stein on all cross-border tax analysis and, in particular, on the integration of the German tax considerations section of the prospectus with the US federal income tax considerations section. For the avoidance of doubt, all German domestic tax law advice remains the sole responsibility of Bähr Stein; the Firm does not provide advice on German tax law.
3. Scope of Tax Advisory Services
The Tax Advisory Services to be provided by Mr. Cross and the Firm's Tax Practice Group in connection with the Offering shall encompass the workstreams described in Sections 3.1 through 3.6 below. The scope described herein is intended to be comprehensive with respect to the anticipated US federal income tax issues arising in connection with the Offering; however, if additional US federal income tax issues are identified during the course of the engagement, the parties may agree in writing to expand the scope of this Supplement accordingly.
3.1 Passive Foreign Investment Company (PFIC) Analysis
Mr. Cross will conduct a comprehensive analysis of Halcyon's status as a "passive foreign investment company" ("PFIC") within the meaning of Sections 1291 through 1298 of the Internal Revenue Code of 1986, as amended (the "Code"). The PFIC analysis is a critical component of the US federal income tax disclosure in the prospectus, as PFIC status would have significant adverse US federal income tax consequences for US holders of ADSs. The PFIC analysis will encompass the following:
(a) Fiscal Years Covered. The analysis will cover Halcyon's fiscal years ended December 31, 2023 ("FY2023"), December 31, 2024 ("FY2024"), and December 31, 2025 ("FY2025", unaudited), with reference to such financial data as may be provided by the Company and its auditors.
(b) Income Test. Application of the income test set forth in Section 1297(a)(1) of the Code, which requires a determination of whether 75% or more of Halcyon's gross income for the taxable year constitutes "passive income" within the meaning of Section 1297(b) of the Code. For this purpose, passive income generally includes dividends, interest, royalties, rents, annuities, and net gains from the sale of property giving rise to such income, subject to certain exceptions. Mr. Cross will analyze the character of each significant category of Halcyon's gross income for each of the three fiscal years under review, with particular attention to income from licensing of semiconductor intellectual property, intercompany royalty arrangements, and investment returns.
(c) Asset Test. Application of the asset test set forth in Section 1297(a)(2) of the Code, which requires a determination of whether the average percentage of assets held by Halcyon during the taxable year that produce passive income or are held for the production of passive income is 50% or more of the total assets of Halcyon. For a publicly traded foreign corporation, the asset test is generally applied on a fair market value basis. Mr. Cross will analyze the composition of Halcyon's asset base, including cash and cash equivalents, working capital, intellectual property, and operating assets, for each of the three fiscal years under review.
(d) Active Business Exception. Preliminary analysis conducted during the engagement scoping process indicates that less than 25% of Halcyon's gross income is passive in character and less than 50% of Halcyon's assets produce or are held for the production of passive income, such that Halcyon is not expected to be classified as a PFIC for any of the fiscal years under review. The PFIC analysis will include a detailed evaluation of this preliminary conclusion, including sensitivity analyses where appropriate, and consideration of any facts or circumstances that might alter the conclusion in future taxable years.
(e) Look-Through Rules for Subsidiaries. Under Section 1297(c) of the Code, in determining the PFIC status of a tested foreign corporation that owns (directly or indirectly) at least 25% by value of the stock of another corporation, the tested foreign corporation is treated as if it held its proportionate share of the assets of the subsidiary corporation and received directly its proportionate share of the income of the subsidiary corporation. Mr. Cross will apply these look-through rules with respect to each of the following subsidiaries of Halcyon:
(i) Halcyon Semiconductor USA Inc. (Delaware corporation);
(ii) Halcyon Power Solutions GmbH (German limited liability company);
(iii) Halcyon Asia Pacific Pte. Ltd. (Singapore private limited company);
(iv) Halcyon Shanghai Semiconductor Co., Ltd. (People's Republic of China limited liability company); and
(v) Halcyon Automotive Components s.r.o. (Czech Republic limited liability company).
(f) Internal PFIC Memorandum. Mr. Cross will prepare a detailed internal memorandum documenting the PFIC analysis and conclusions for each of FY2023, FY2024, and FY2025, together with supporting calculations, assumptions, and data sources. This memorandum is intended for the Company's internal records and for reference by the working group, and is not intended for distribution to investors or inclusion in the Registration Statement.
(g) Future Year PFIC Implications. The PFIC analysis section of the prospectus will include a discussion of the implications for US holders of ADSs in the event that PFIC status were to apply in any future taxable year, including a description of the excess distribution regime under Section 1291 of the Code, the availability and consequences of a qualified electing fund ("QEF") election under Section 1295 of the Code, and the availability and consequences of a mark-to-market election under Section 1296 of the Code.
3.2 US Federal Income Tax Opinion for Prospectus
Mr. Cross will prepare a tax opinion (the "Tax Opinion") regarding the material US federal income tax consequences of the acquisition, ownership, and disposition of ADSs by US holders (as defined in the prospectus). The Tax Opinion will be prepared in accordance with the standards and requirements applicable to tax opinions filed in connection with registered offerings under the Securities Act and will address the following key topics:
(a) Classification of ADSs. The Tax Opinion will address the classification of the ADSs as equity for US federal income tax purposes, including the treatment of holders of ADSs as the owners of the underlying ordinary shares of Halcyon for US federal income tax purposes, consistent with established IRS guidance and case law regarding the tax treatment of American Depositary Shares.
(b) Distributions on ADSs. The Tax Opinion will address the US federal income tax treatment of distributions made on the ADSs, including the characterization of such distributions as dividends (to the extent paid out of the Company's current or accumulated earnings and profits as determined for US federal income tax purposes), return of capital (to the extent in excess of earnings and profits), or capital gain. The Tax Opinion will also address the translation of euro-denominated distributions into US dollars for tax purposes and any foreign currency gain or loss that may arise as a result of such translation.
(c) Qualified Dividend Income. The Tax Opinion will address the eligibility of dividends paid on the ADSs for the reduced rates of tax applicable to "qualified dividend income" under Section 1(h)(11) of the Code for individual US holders and certain other non-corporate US holders. This analysis will take into account, among other factors, the requirement that Halcyon not be a PFIC for the taxable year in which the dividend is paid or the preceding taxable year, and the requirement that certain holding period conditions be satisfied.
(d) PFIC Conclusions. The Tax Opinion will include a discussion of the Company's PFIC status, cross-referencing the PFIC analysis described in Section 3.1 above, and will describe the consequences to US holders if the Company were to be classified as a PFIC in any future taxable year.
(e) Disposition of ADSs. The Tax Opinion will address the US federal income tax consequences of a sale, exchange, or other taxable disposition of ADSs by a US holder, including the recognition of capital gain or loss, the determination of the holding period for purposes of distinguishing between long-term and short-term capital gain or loss, and the determination of the US holder's tax basis in the ADSs.
(f) Foreign Currency Gain or Loss. The Tax Opinion will address any foreign currency gain or loss that may be recognized by a US holder on the receipt of euro-denominated distributions on the ADSs, including the application of Section 988 of the Code to such transactions.
(g) Information Reporting and Backup Withholding. The Tax Opinion will address the information reporting obligations and backup withholding requirements under Section 3406 of the Code that may apply to distributions on, and proceeds from the sale or other disposition of, ADSs held by US holders.
(h) FATCA. The Tax Opinion will address the potential application of the Foreign Account Tax Compliance Act ("FATCA"), as codified in Sections 1471 through 1474 of the Code, and the Treasury Regulations and IRS guidance thereunder, to payments made with respect to the ADSs. The analysis will consider the applicability of the US-Germany intergovernmental agreement (the "IGA") implementing FATCA in Germany.
(i) Filing and Inclusion in Prospectus. The Tax Opinion, or a summary thereof, is intended to be included in the "Taxation" section of the prospectus forming part of the Registration Statement on Form F-1. To the extent required by applicable SEC rules and guidance, including Item 601(b)(8) of Regulation S-K, the Tax Opinion will also be filed as an exhibit to the Registration Statement.
(j) Coordination with German Tax Section. Mr. Cross will coordinate with Bähr Stein Rechtsanwälte with respect to the German tax considerations section of the prospectus to ensure consistency between the US and German tax disclosure. Mr. Cross will review and provide comments on the German tax section drafted by Bähr Stein and will work with Bähr Stein to integrate the two sections into a cohesive "Taxation" chapter for the prospectus.
3.3 US/German Tax Treaty Analysis
Mr. Cross will conduct a detailed analysis of the Convention Between the United States of America and the Federal Republic of Germany for the Avoidance of Double Taxation and the Prevention of Fiscal Evasion with Respect to Taxes on Income and Capital and to Certain Other Taxes, signed on August 29, 1989, as amended by the Protocol signed on June 1, 2006 (the "Treaty"), as it applies to the Offering and to the ownership of ADSs by US holders. The Treaty analysis will address the following matters:
(a) Treaty Article 10 — Dividends. A detailed analysis of Article 10 of the Treaty, which governs the taxation of dividends paid by a German company to a US resident. Under current German domestic law, dividends paid by a German corporation are subject to German withholding tax at a statutory rate of 26.375%, comprising the 25% capital gains withholding tax (Kapitalertragsteuer) and the 5.5% solidarity surcharge (Solidaritätszuschlag) thereon. Under Article 10(2)(b) of the Treaty, the rate of German withholding tax on dividends paid to a qualifying US resident is reduced to 15% (or, in certain cases, 5% for corporate shareholders holding at least 10% of the voting stock of the paying company). Mr. Cross will analyze the conditions under which US holders of ADSs will be eligible for the reduced treaty rate.
(b) Limitation on Benefits. The Treaty contains a comprehensive Limitation on Benefits ("LOB") article (Article 28), which imposes requirements on US residents seeking to claim treaty benefits. Mr. Cross will analyze the LOB provisions as applied to various categories of US holders, including individual US holders, US corporations, US partnerships, US pension funds (including 401(k) plans and individual retirement accounts), and US tax-exempt organizations described in Section 501(c)(3) of the Code. The analysis will identify any categories of US holders that may not qualify for treaty benefits under the LOB article and will discuss the implications for such holders.
(c) US Foreign Tax Credit Analysis. Mr. Cross will analyze the creditability of German withholding taxes paid by US holders of ADSs against their US federal income tax liability, including the application of Section 901 of the Code (which allows a credit for income taxes paid or accrued to a foreign country) and Section 904 of the Code (which limits the foreign tax credit to the US tax attributable to foreign source income). The analysis will address the appropriate separate limitation basket classification for dividends received on the ADSs, including whether such dividends constitute "passive category income" or "general category income" for purposes of Section 904(d) of the Code.
(d) ADS Structure Considerations. The analysis will address potential issues arising from the ADS structure — specifically, the fact that the depositary (Meridian Trust) holds the underlying ordinary shares on behalf of ADS holders — on the entitlement of US holders to claim treaty benefits with respect to German withholding tax. The analysis will consider whether the interposition of the depositary as a registered holder of the underlying shares creates any impediment to the flow-through of treaty benefits to the beneficial owners of the ADSs.
(e) Internal Treaty Memorandum. Mr. Cross will prepare a detailed internal memorandum summarizing the Treaty analysis and conclusions set forth above. This memorandum is intended for the Company's internal records and for reference by the working group, and is not intended for distribution to investors or inclusion in the Registration Statement.
3.4 Qualified Intermediary (QI) Analysis for Meridian Trust Company, N.A.
Mr. Cross will conduct an analysis of the qualified intermediary ("QI") status and obligations of Meridian Trust Company, N.A. (principal office at 101 Barclay Street, New York, NY 10286; contact: Patricia Novak, Vice President, Depositary Receipts) in connection with the Offering and the ongoing administration of the ADS program. The QI analysis will encompass the following:
(a) QI Status. Analysis of Meridian Trust's status as a Qualified Intermediary under the QI Agreement framework established by Revenue Procedure 2017-15, as amended by subsequent revenue procedures and IRS guidance. Mr. Cross will review Meridian Trust's current QI Agreement with the IRS and confirm that Meridian Trust's QI status is in good standing and covers the types of payments expected to be made in connection with the ADS program.
(b) Withholding Responsibilities. Evaluation of Meridian Trust's primary withholding responsibilities with respect to German Kapitalertragsteuer on dividend distributions paid to ADS holders through the depositary arrangement. The analysis will consider the extent to which Meridian Trust, as depositary and QI, is required to withhold German tax at source or is entitled to apply the reduced treaty rate on behalf of US ADS holders for whom appropriate documentation is on file.
(c) Interaction of German Withholding, QI Framework, and Deposit Agreement. Analysis of the interaction among: (i) German withholding tax procedures applicable to dividends paid by Halcyon on the ordinary shares deposited with the depositary; (ii) the QI framework and Meridian Trust's obligations thereunder; and (iii) the Deposit Agreement (which is expected to be governed by the laws of the State of Delaware) through which ADS holders receive distributions. The analysis will identify any procedural or structural issues that could affect the ability of US ADS holders to receive the benefit of the reduced treaty withholding rate at source, as opposed to being required to file for a refund of excess withholding.
(d) Documentation Requirements. Assessment of the documentation requirements that Meridian Trust must satisfy in order to claim treaty benefits on behalf of US ADS holders, including the collection and maintenance of IRS Forms W-8 and W-9 from ADS holders and DTC participants, and any corresponding German tax documentation.
(e) Coordination with German Counsel. Mr. Cross will coordinate with Bähr Stein Rechtsanwälte regarding the procedures of the German Federal Central Tax Office (Bundeszentralamt für Steuern) for granting treaty relief at source or processing refund claims for excess German withholding tax. This coordination will ensure that the QI analysis is consistent with German procedural requirements.
(f) Internal QI Memorandum. Mr. Cross will prepare a memorandum documenting the QI analysis and recommendations, including any operational steps that Meridian Trust or the Company should take to ensure that the reduced treaty rate is available to eligible US ADS holders. This memorandum is intended for the Company's internal records and for reference by the working group.
3.5 Treaty Benefit Certification Procedures for US ADS Holders
Mr. Cross will analyze the documentation and certification procedures applicable to US ADS holders seeking to claim the reduced 15% treaty withholding rate on dividends paid on the ADSs, and will prepare related recommendations and disclosure materials. This workstream will encompass the following:
(a) IRS Documentation Requirements. Analysis of the IRS documentation requirements for US ADS holders to certify their status as US residents eligible for treaty benefits, including the applicable provisions of Treasury Regulations under Sections 1441 through 1446 of the Code and the QI Agreement.
(b) Forms W-8BEN and W-8BEN-E. Review of the requirements applicable to IRS Form W-8BEN (Certificate of Foreign Status of Beneficial Owner for United States Tax Withholding and Reporting — for individuals) and IRS Form W-8BEN-E (Certificate of Status of Beneficial Owner for United States Tax Withholding and Reporting — for entities), as they apply to US ADS holders claiming treaty benefits under the Treaty. The analysis will distinguish between the documentation required from individual and entity holders and will address any special considerations applicable to particular categories of entity holders (e.g., partnerships, trusts, and pension funds).
(c) Certification Chain. Analysis of the certification chain through which treaty benefit claims flow from the beneficial owner of the ADSs through the relevant intermediaries, including: (i) the ADS holder; (ii) the DTC participant through which the ADS holder holds its position; (iii) Crestfield Transfer Services Inc. (transfer agent and registrar for the ADSs, located at 6201 15th Avenue, Brooklyn, NY 11219; contact: Angela Moretti, Director, Corporate Actions); and (iv) Meridian Trust as depositary. The analysis will identify any breaks or weaknesses in the certification chain that could impede the flow-through of treaty benefits.
(d) Certification Procedures Memorandum. Mr. Cross will prepare a memorandum describing the certification procedures and recommending appropriate disclosure for inclusion in the prospectus (in the "Taxation" section) to inform US ADS holders of the documentation steps required to claim the reduced treaty rate.
(e) Form W-8BEN-E for Halcyon Semiconductor AG. Mr. Cross will draft or review IRS Form W-8BEN-E for Halcyon Semiconductor AG itself, to be used by the Company in connection with its interactions with US withholding agents and financial institutions. The Form W-8BEN-E will include the Company's entity classification for US federal income tax purposes, the Company's FATCA status and applicable FATCA exemption code, and the Company's Legal Entity Identifier ("LEI"): 5299007KBTVZ3XQHGL48. This form will be prepared in accordance with the instructions to Form W-8BEN-E and applicable Treasury Regulations.
3.6 Additional Tax Advisory Matters
In addition to the principal workstreams described in Sections 3.1 through 3.5, Mr. Cross will provide advisory services on the following additional US federal income tax matters arising in connection with the Offering:
(a) Tax-Related Risk Factors. Review of and comment on the tax-related risk factors to be included in the prospectus, including risk factors relating to PFIC status, changes in US or German tax law, and the availability of treaty benefits.
(b) Selling Shareholder Withholding. Advice on the US withholding tax implications, if any, for the selling shareholders participating in the Offering, specifically Rheintal Industrieholding GmbH (a German limited liability company) and Kestrel Capital Partners AG (a Swiss stock corporation). Both selling shareholders are non-US entities, and the analysis will address whether any US withholding tax obligations arise in connection with the sale of ADSs by such entities in the Offering.
(c) Use of Proceeds. Review of any US tax implications arising from the Company's intended use of the net proceeds of the Offering, including the proposed repayment of approximately $100,000,000 of the revolving credit facility tranche, and advice on whether any such use of proceeds gives rise to US federal income tax consequences that should be disclosed in the prospectus.
(d) US Subsidiary Tax Reporting. Advice on any US tax reporting obligations arising from the Company's US subsidiary, Halcyon Semiconductor USA Inc. (a corporation organized under the laws of the State of Delaware; Employer Identification Number: 84-3927561; principal office at 2500 Augustine Drive, Suite 100, Santa Clara, CA 95054), including any information reporting obligations that may be triggered or affected by the Offering.
(e) Transfer Pricing. Advice on any transfer pricing considerations relevant to prospectus disclosure, including the disclosure of material intercompany transactions between Halcyon and its subsidiaries that could give rise to transfer pricing adjustments or disputes with tax authorities, to the extent such matters are material to the US federal income tax analysis.
(f) FIRPTA. Advice on any considerations arising under the Foreign Investment in Real Property Tax Act ("FIRPTA"), as codified in Sections 897 and 1445 of the Code, to the extent applicable to the Company, the ADSs, or the Offering. In particular, Mr. Cross will evaluate whether Halcyon could be classified as a "United States real property holding corporation" within the meaning of Section 897(c)(2) of the Code, and, if so, the implications for US holders of ADSs upon a disposition of their interests.
4. Deliverables
Mr. Cross will prepare and deliver the following work product in connection with the Tax Advisory Services described in this Supplement. All target delivery dates are subject to the overall transaction timeline and may be adjusted by mutual agreement of the parties in consultation with the Capital Markets team:
1. PFIC Analysis Memorandum (Internal). A detailed internal memorandum documenting the PFIC analysis and conclusions for FY2023, FY2024, and FY2025, together with supporting calculations, assumptions, and data sources. Target Delivery Date: Prior to circulation of the first draft of the Registration Statement on Form F-1 (March 9, 2026).
2. US/German Tax Treaty Memorandum (Internal). A detailed internal memorandum summarizing the analysis of the Treaty as applied to the Offering and the ownership of ADSs by US holders, including the LOB analysis, foreign tax credit analysis, and ADS structure considerations. Target Delivery Date: Prior to circulation of the first draft of the Registration Statement on Form F-1 (March 9, 2026).
3. Draft Prospectus Taxation Section (US Federal Income Tax Consequences). A draft of the "US Federal Income Tax Consequences" section of the prospectus, covering all topics described in Section 3.2 of this Supplement. This draft will be prepared for incorporation into the first draft of the Form F-1. Target Delivery Date: To be incorporated in the first draft of the Registration Statement on Form F-1 (March 9, 2026).
4. QI Analysis Memorandum (Internal). A memorandum documenting the analysis of Meridian Trust's QI status, withholding responsibilities, and operational recommendations. Target Delivery Date: By the all-parties drafting session (March 23–24, 2026).
5. Treaty Benefit Certification Procedures Memorandum (Internal). A memorandum describing the documentation and certification procedures applicable to US ADS holders claiming the reduced treaty withholding rate, including recommendations for prospectus disclosure. Target Delivery Date: By the all-parties drafting session (March 23–24, 2026).
6. Draft IRS Form W-8BEN-E for Halcyon Semiconductor AG. A completed or substantially completed draft of IRS Form W-8BEN-E for the Company, including entity classification, FATCA status, and LEI. Target Delivery Date: By the confidential submission date for the Registration Statement (April 14, 2026).
7. Final Tax Opinion for Filing with Registration Statement. The final Tax Opinion for filing as an exhibit to the Registration Statement on Form F-1, addressing the material US federal income tax consequences of the acquisition, ownership, and disposition of ADSs by US holders. Target Delivery Date: Prior to the SEC declaration of effectiveness of the Registration Statement (June 22, 2026).
The foregoing deliverables are also set forth in summary table format in Exhibit A attached hereto.
5. Limitations and Exclusions
The Tax Advisory Services described in this Supplement are subject to the following limitations and exclusions:
(a) Scope of Tax Law Coverage. The Tax Advisory Services are limited to US federal income tax law and the US-Germany income tax treaty (the Treaty). All advice on German domestic tax law, including German withholding tax procedures, German corporate tax, German trade tax (Gewerbesteuer), and German value added tax, is the exclusive responsibility of Bähr Stein Rechtsanwälte. Calderwood & Harkness does not provide tax advice under the laws of Germany.
(b) Other Jurisdictions. Calderwood & Harkness does not provide tax advice under the laws of Switzerland (relevant to the selling shareholder Kestrel Capital Partners AG), the Republic of Singapore (relevant to the subsidiary Halcyon Asia Pacific Pte. Ltd.), the People's Republic of China (relevant to the subsidiary Halcyon Shanghai Semiconductor Co., Ltd.), or the Czech Republic (relevant to the subsidiary Halcyon Automotive Components s.r.o.). If tax advice under the laws of any of these jurisdictions is required, the Company should retain separate local counsel with expertise in the applicable tax law. Calderwood & Harkness will cooperate with any such local counsel as reasonably requested.
(c) State and Local Tax. Unless otherwise specifically agreed in writing, the Tax Advisory Services do not include advice on US state or local income, franchise, or other tax law matters. The Tax Opinion for the prospectus will address only US federal income tax consequences and will include a customary disclaimer regarding state and local tax consequences.
(d) Currency of Legal Authority. All tax opinions, memoranda, and other work product delivered pursuant to this Supplement are based upon the Code, Treasury Regulations promulgated thereunder, IRS rulings and administrative guidance, judicial decisions, and the Treaty, in each case as in effect on the date of issuance. Tax law is subject to change, potentially with retroactive effect, and no assurance can be given that the law will not change in a manner that could alter the conclusions set forth in any opinion or memorandum.
(e) No Assurance of IRS Agreement. No assurance can be given that the Internal Revenue Service ("IRS") will agree with any position or conclusion set forth in any tax opinion or memorandum delivered pursuant to this Supplement, or that a court of competent jurisdiction would sustain any such position or conclusion if challenged. The Tax Opinion is not a guarantee of any particular tax result.
(f) Customary Assumptions and Qualifications. The Tax Opinion for the prospectus will be subject to customary assumptions and qualifications, including, without limitation, assumptions regarding the accuracy and completeness of the representations and information provided by the Company, the enforceability of relevant agreements, and the absence of changes in law after the date of the opinion.
6. Fee Arrangements
All Tax Advisory Services provided pursuant to this Supplement will be billed on an hourly basis at the rates set forth in the Engagement Letter dated January 12, 2026. For the avoidance of doubt:
(a) Leonard Cross Billing Rate. Mr. Cross's current billing rate is $1,900 per hour, as set forth in the Engagement Letter. Time spent by Mr. Cross on the Tax Advisory Services will be recorded and billed in accordance with the Firm's standard timekeeping and billing practices.
(b) Additional Tax Personnel. Any additional tax associates or of-counsel attorneys assigned to the engagement will be billed at their applicable rates as set forth in the Engagement Letter or as otherwise communicated to the Company in writing prior to the commencement of such personnel's work on the engagement.
(c) Inclusion in Total Fee Estimate. The fees for the Tax Advisory Services are included within the estimated total legal fees of $3,200,000 to $3,800,000 set forth in the Engagement Letter. There is no separate retainer or fee estimate for the Tax Advisory Services apart from the overall engagement fee estimate. As noted in the Engagement Letter, the fee estimate is a good-faith projection based on the anticipated scope of the engagement and is not a cap or guarantee.
(d) Application of Retainer. The retainer of $250,000 received by the Firm upon execution of the Engagement Letter applies to all services provided under the Engagement Letter, including the Tax Advisory Services described herein. The retainer will be applied against invoices for services rendered in the ordinary course, as set forth in the Engagement Letter.
7. Coordination with Other Advisors
In connection with the Tax Advisory Services, Mr. Cross will coordinate directly with the following external advisors and Company personnel:
(a) Bähr Stein Rechtsanwälte Partnerschaftsgesellschaft mbB. Dr. Christoph Maurelban, Partner, Capital Markets, and Johanna Weiß, Senior Associate, for German tax law matters and the German tax considerations portion of the prospectus. As described above, Mr. Cross will review and comment on the German tax disclosure prepared by Bähr Stein and will work with Bähr Stein to ensure consistency between the US and German tax sections of the prospectus and to coordinate cross-border tax analysis, including Treaty analysis and German withholding tax procedures.
(b) Blackmere & Whitfield LLP / GmbH WPG (Auditors). Dieter Kaufmann, Wirtschaftsprüfer, Munich office, and Graham Templeton, Partner, New York office. Mr. Cross will coordinate with Blackmere & Whitfield regarding financial data to be used in the PFIC analysis, including gross income breakdowns, asset composition data, and subsidiary financial statements. Mr. Cross will also coordinate with Blackmere & Whitfield regarding any tax-related items to be addressed in the accountants' comfort letter, including the agreement of tax-related numerical data in the prospectus to underlying financial records.
(c) Meridian Trust Company, N.A. Patricia Novak, Vice President, Depositary Receipts. Mr. Cross will coordinate with Meridian Trust regarding QI status documentation, depositary withholding procedures, and the operational mechanics of applying the reduced treaty withholding rate to dividend distributions through the ADS program.
(d) Halcyon Internal Contacts. Katarina Dalmqvist, Chief Financial Officer (Finanzvorstand), and Halcyon's internal tax department. Mr. Cross will coordinate with Ms. Dalmqvist and the Company's tax team for company-specific financial and operational data necessary for the PFIC analysis, Treaty analysis, and withholding analyses, including revenue classification data, intercompany transaction records, asset valuations, subsidiary financial statements, and any prior tax rulings or correspondence with tax authorities relevant to the scope of the Tax Advisory Services.
8. Governing Terms
This Supplement is governed by and subject to all terms, conditions, and provisions of the Engagement Letter dated January 12, 2026, including, without limitation, the provisions relating to:
(a) confidentiality and the protection of privileged communications;
(b) conflicts of interest and the Firm's conflict clearance procedures;
(c) limitation of liability;
(d) dispute resolution, including any arbitration or mediation provisions;
(e) the governing law and jurisdiction provisions; and
(f) the termination provisions.
In the event of any conflict or inconsistency between this Supplement and the Engagement Letter, the Engagement Letter shall control in all respects, except that this Supplement shall control with respect to the specific scope of Tax Advisory Services to be provided by Mr. Cross and the Firm's Tax Practice Group, including the deliverables and target delivery dates set forth herein.
This Supplement may be amended, modified, or supplemented only by a written instrument signed by an authorized representative of each of Calderwood & Harkness and Halcyon.
9. Counterparts and Acknowledgment
This Supplement may be executed in one or more counterparts (including by means of electronic signatures transmitted by email or electronic signature platform), each of which shall be deemed an original and all of which, taken together, shall constitute one and the same instrument.
We respectfully request that Mr. Ostermann, in his capacity as General Counsel (Chefjustitiar) of Halcyon Semiconductor Aktiengesellschaft, indicate Halcyon's agreement to the terms of this Supplement by executing and returning the countersignature block below. A copy of this Supplement, fully executed by both parties, will be retained in the Firm's files and a copy will be provided to the Company for its records.
We look forward to continuing our work with Halcyon and its advisors on this important transaction. Should you have any questions regarding the scope of the Tax Advisory Services described herein, please do not hesitate to contact Leonard Cross at lcross@calderwoodharkness.com or +1 (212) 555-7438, or Vivienne St. Claire at vstclaire@calderwoodharkness.com or +1 (212) 555-7422.
Very truly yours,
CALDERWOOD & HARKNESS LLP
By: ________
Name: Vivienne St. Claire
Title: Partner, Capital Markets
(Responsible Partner for the Engagement)
By: ________
Name: Leonard Cross
Title: Partner, Tax
(Tax Advisory Lead)
ACKNOWLEDGED AND AGREED
The undersigned, acting on behalf of Halcyon Semiconductor Aktiengesellschaft, hereby acknowledges receipt of this Supplement and agrees to the terms and conditions set forth herein.
HALCYON SEMICONDUCTOR AKTIENGESELLSCHAFT
By: ________
Name: Wilhelm Ostermann
Title: General Counsel (Chefjustitiar)
Date: ________
EXHIBIT A
Summary of Tax Advisory Workstreams and Target Delivery Schedule
The following table summarizes the Tax Advisory Services deliverables described in Section 4 of this Supplement. The "Status" column is provided for the working group's internal tracking purposes and is intentionally left blank at the time of execution of this Supplement.
This Exhibit A is provided for convenience of reference only and is qualified in its entirety by the detailed descriptions of each workstream set forth in Sections 3 and 4 of this Supplement.
No. | Workstream | Description | Lead Attorney | Target Delivery Date | Status
1 | PFIC Analysis Memorandum (Internal) | Detailed internal memorandum documenting PFIC analysis and conclusions for FY2023, FY2024, and FY2025, with supporting calculations | Leonard Cross | March 9, 2026 (prior to first draft F-1 circulation)
2 | US/German Tax Treaty Memorandum (Internal) | Internal memorandum summarizing Treaty analysis, LOB analysis, foreign tax credit analysis, and ADS structure considerations | Leonard Cross | March 9, 2026 (prior to first draft F-1 circulation)
3 | Draft Prospectus Taxation Section (US Federal Income Tax Consequences) | Draft of the "US Federal Income Tax Consequences" section of the prospectus for incorporation in the first draft F-1 | Leonard Cross | March 9, 2026 (incorporated in first draft F-1)
4 | QI Analysis Memorandum (Internal) | Memorandum documenting analysis of Meridian Trust's QI status, withholding responsibilities, and operational recommendations | Leonard Cross | March 23–24, 2026 (all-parties drafting session)
5 | Treaty Benefit Certification Procedures Memorandum (Internal) | Memorandum on documentation and certification procedures for US ADS holders claiming reduced treaty withholding rate; includes prospectus disclosure recommendations | Leonard Cross | March 23–24, 2026 (all-parties drafting session)
6 | Draft IRS Form W-8BEN-E for Halcyon Semiconductor AG | Completed or substantially completed draft of IRS Form W-8BEN-E for the Company (entity classification, FATCA status, LEI: 5299007KBTVZ3XQHGL48) | Leonard Cross | April 14, 2026 (confidential submission date)
7 | Final Tax Opinion for Filing with Registration Statement | Final Tax Opinion addressing material US federal income tax consequences of acquisition, ownership, and disposition of ADSs by US holders; for filing as exhibit to Form F-1 | Leonard Cross | June 22, 2026 (prior to SEC declaration of effectiveness)

CALDERWOOD & HARKNESS LLP Attorneys at Law

VIA EMAIL AND INTERNATIONAL COURIER

CALDERWOOD & HARKNESS LLP

ACKNOWLEDGED AND AGREED

HALCYON SEMICONDUCTOR AKTIENGESELLSCHAFT

EXHIBIT A

Record

Parties

Dates

Amounts