Marsh & McLennan Cos., the largest insurance broker by market value, agreed to buy SCM Strategic Capital Management AG as its Mercer unit expands in alternative investments.

SCM, which oversees $4 billion, focuses on advising institutional clients on investments like private equity and real estate, London-based Mercer said today in a statement that didn’t disclose terms. The entire investment team, including SCM Chief Executive Officer Stefan Hepp, will join Mercer, the firm said.

Mercer is seeking to increase its alternative-asset business as more clients look for investments beyond stocks and bonds. The unit oversaw $108 billion, including $13 billion in alternatives, at the end of September.

“Increasingly our investment clients are seeking advice regarding alternatives investment strategy, either through a custom portfolio or a delegated solution,” Phillip de Cristo, president of Mercer Investments, said in the statement.

The transaction is expected to be completed in the first quarter of next year, according to the statement.

Marsh gained 1 percent to $56.39 at 9:31 a.m. in New York. The shares have climbed 17 percent this year, outpacing the 11 percent advance of the 85-company Standard & Poor’s 500 Financial Index.