Ken Griffin, the founder of Citadel, has significantly increased his stake in Sphere Entertainment to 5.3%, according to a recent SEC filing. Having previously held a 1.6% stake in Sphere through Citadel, Griffin added more than 900,000 shares since April 1, bringing his total holdings to 1.5 million shares.

Griffin’s investment coincides with a similar move by another hedge fund titan, Steve Cohen. Last month, Cohen, the owner of the New York Mets, disclosed a new 5.5% stake in Sphere Entertainment through his hedge fund, Point72 Asset Management. This aligns Cohen with Jim Dolan, who has voting control of the Sphere and also owns the New York Knicks and New York Rangers through Madison Square Garden Sports.

The Dolan family holds 8.5 million shares of Sphere Entertainment. Other major institutional shareholders include Ariel Investments, Vanguard Group, and Jericho Capital Asset Management. Dolan recently secured three-year contract extensions to continue managing Sphere, MSG Sports, and MSG Entertainment.

In addition to his stake in Sphere, Griffin previously explored purchasing a minority stake in the Miami Dolphins, Hard Rock Stadium, and the F1 Miami Grand Prix from Stephen Ross, although the deal did not materialize.

Sphere Entertainment’s $2.3bn venue, which opened in September, with a 4run of 40 U2 concerts, followed by performances from Phish, Dead & Company, and the Eagles, has also hosted the NHL Draft and will host UFC 306 in late September.