DIGITAL MANUFACTURING. REIMAGINED.

Transaction Summary Presenters Ryan Martin Chief Executive Officer, Fathom Transaction Highlights Altimar Acquisition Corp. II 然 Altimar Acquisition Corp. II (NYSE: ATMR) is a publicly listed special purpose acquisition company with $345mm in cash • $80mm PIPE commitments before transaction announcement Rich Stump Co-Founder & Chief Commercial Officer, Fathom Valuation • • $1.5bn pro forma enterprise value with a strong balance sheet Implied 27.5x 2022E EBITDA of $54mm and 7.3x 2022E Revenue of $205mm offers an attractive valuation relative to the peer group Mark Frost Chief Financial Officer, Fathom Tom Wasserman Capital Structure Pre-transaction, Fathom is already a positive, self-sustaining cash flow business Total pro forma liquidity of $62mm¹ Post-transaction, PF net leverage of 2.85x gives the Company sufficient firepower to continue pursuing its M&A strategy Expected net leverage multiple of 1.50x as of FYE 2022E CEO / Chairman, Altimar Acquisition Corp. II; Managing Director, HPS Investment Partners, LLC Ownership 64% existing shareholders; 30% SPAC shareholders and sponsor founder shares; 6% PIPE investors² 1 $37mm of pro forma cash as of 3/31/2021 plus $25mm of availability under a new $50mm revolving credit facility. On April 30, 2021, Fathom completed a financing transaction in which it entered into a $172 million term loan due April 2022 (the "April 2021 Term Loan") in order to finance certain acquisitions and to refinance Fathom's existing debt. Fathom is entering a new credit facility that will become effective upon the closing of the Transaction. The new credit facility includes a $50 million revolving credit facility and a $125 million term loan that mature in 2026. Fathom intends to use proceeds from this credit facility to repay the April 2021 Term Loan; 2 See slide 31 "Detailed transaction overview" for key assumptions and additional details. Assumes no redemptions by Altimar Acquisition Corp. II's existing public shareholders FATHOM Fathom Proprietary and Confidential 4

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