Capital One said Thursday that it was acquiring payments startup Brex for $5.15 billion, the latest splashy deal undertaken by the bank’s CEO, Richard Fairbank.

The firm, which disclosed the deal in its fourth-quarter earnings statementsaid the deal is made up of 50% cash and 50% stock. Brex was previously valued at $12.3 billion.

Shares of the bank fell about 3%.

Under Fairbank, a rare founder-CEO of a major U.S. bank, Capital One acquired rival card firm Discover Financial last year for about $35 billion. That deal was Fairbank’s crowning achievement, giving the credit card lender access to one of the only payment networks of any scale.

“Since our founding, we set out to build a payments company at the frontier of the technology revolution,” Fairbank said in a release. “Acquiring Brex accelerates this journey, especially in the business payments marketplace.”

Fairbank said that Brex pioneered the combination of corporate cards, banking and spend management software: “They have taken the rarest of journeys for a fintech, building a vertically integrated platform from the bottom of the tech stack to the top.”

Still, the more than 50% decline in valuation for Brex from its 2023 level shows the headwinds that even successful fintech companies have encountered.

Brex is among a class of fintech firms that rose to prominence during a period of low interest rates; it was known initially as a startup that made loans to other startups via its cards.

But the company expanded beyond technology into other sectors and now services larger established firms and startups alike, including Robinhood, Zoom and Anthropic.

Capital One, which has offered business credit cards for decades, became increasingly convinced that it was Brex’s model that would be the winning offering, according to a person with knowledge of the lender’s strategy.

“We didn’t have to pursue this acquisition, our growth was incredibly strong,” Brex CEO Pedro Franceschi told CNBC in an interview.

Combining Brex’s technology with Capital One’s reach and resources would grow the startup’s scale faster than as a standalone firm, he said.