The Calpers pension fund is moving further into trailblazing territory, taking a roughly 10% stake in private-equity firm Silver Lake, the Wall Street Journal reports.

The value of the stake in Silver Lake — which makes large investments in technology companies — wasn’t disclosed.

With assets totaling nearly $250 billion, the California Public Employees’ Retirement System has the financial firepower to push for creative deals and terms. In adding the stake in Silver Lake, which has its main offices in Menlo Park, Calif., and New York, Calpers now has a clutch of investments in the world’s leading buyout groups, including a 10% stake in Apollo Management LP and a 5.5% stake in Carlyle Group.

The infusions allow the private-equity groups to get “permanent capital” — money that is separate from the investment funds that must be returned to outside investors. It also sets a valuation on their operations.

Stephen Nesbitt, chief executive of Cliffwater LLC, a Marina Del Ray, Calif., consulting firm, says that other than Calpers, it is extremely rare for a pension fund to take a direct stake in a private-equity firm. Depending on the price, Calpers’s move could be shrewd.

“Getting a piece of management is smart because you get part of your fees back and a piece of everyone else’s fees,” Mr. Nesbitt said.

Last year during boom times, a number of large private-equity firms sold stakes in themselves to outsiders. Two presaged stock sales. Before their stock offerings, Apollo sold 10% stakes to Calpers and the Abu Dhabi Investment Authority and Blackstone Group sold less than 10% of its management company to the investment arm of the Chinese government. Carlyle, which hasn’t filed to go public, sold a 7.5% stake to an investment arm of the Abu Dhabi government.

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