T. Rowe Price Group has completed its planned acquisition of New York-based Oak Hill Advisors for $4.2 billion, making its first big expansion into private markets as it looks to grow beyond its better-known mutual fund retirement business.

The Baltimore-based money management firm said Wednesday it acquired 100% of the equity of Oak Hill, an alternative credit manager with $53 billion of capital under management and more than 300 employees worldwide. The deal, announced in October, is T. Rowe’s largest-ever acquisition.

“This acquisition allows us to broaden our private markets business and add new capabilities in an area of tremendous client interest and growth,” said Rob Sharps, T. Rowe president, head of investments and incoming CEO, in an announcement.

Alternative investments in privately owned companies typically include private equity, private lending, venture capital and private real estate assets.

T. Rowe had said it would pay $3.3 billion at closing, including about three-quarters in cash and a quarter in T. Rowe Price common stock, then up to an additional $900 million in cash after achieving certain business milestones starting in 2025.

Oak Hill will operate as a standalone business within T. Rowe Price and maintain its workforce and investment autonomy, T. Rowe said. Glenn August, founder and CEO of Oak Hill, will continue in that role and as of Thursday, joined T. Rowe’s board of directors and management committee.

“Together, we have the ability to deliver even more value to our clients whom we expect to benefit from greater scale and a broader range of product offerings over time,” August said in Wednesday’s announcement.

T. Rowe announced the deal’s completion after the stock market closed Wednesday. Shares of T. Rowe closed Thursday at $198.14.

The company’s stock had gone up 5.7% on the day T. Rowe announced the acquisition in October, a potential sign that the market viewed the deal favorably.

Alternative credit strategies have been in demand globally from institutional and retail investors who are looking for attractive yields and risk-adjusted returns, the company had said. While T. Rowe offers investments in more secure, fixed-income bonds, Oak Hill has a successful track record in consolidating high-risk debt, such as bond issues for struggling companies, which can offer a higher return.