American Tower REIT /zigman2/quotes/200890312/composite AMT +0.46% announced Monday an agreement in which it investment firm Stonepeak will by a 29% stake in American Tower's U.S. data center business in a deal valued at $2.5 billion. That implies a $10.5 billion valuation for American Tower's U.S. data center business. The deal comes about a week after the real estate investment trust (REIT) focused on communications sites said it filed term sheet that considers a third-party minority investment in its data center business. American Tower said the deal with Stonepeak supports the equity financing part of its previously announced completion of its CoreSight Realty Corp. acquisition in late-2021. "We are pleased to partner with Stonepeak in our U.S. data center business, where we expect to create value through growth in our highly interconnected, cloud on-ramp rich portfolio of data center assets," said American Tower Chief Executive Tom Bartlett. American Tower's stock, which was still inactive in premarket trading, has slipped 3.2% over the past three months while the SPDR Real Estate Select Sector ETF /zigman2/quotes/207325179/composite XLRE +1.07% has dropped 15.8% and the S&P 500 /zigman2/quotes/210599714/realtime SPX -1.51% has lost 11.6%.