Nebius, which was spun out from Russian internet giant Yandex, provides graphics processing units or GPUs for training artificial intelligence models.Sopa Images | Lightrocket | Getty ImagesDutch cloud provider Nebius popped in premarket trading Thursday after an ex-OpenAI employee's fund disclosed a sizeable stake in the firm. Situational Awareness, a hedge fund founded by former OpenAI researcher Leopold Aschenbrenner, now owns 12.4 million Class A shares of the AI firm, according to a filing published on Wednesday. That represents a 5.6% stake.Situational Awareness manages billions in funds and invests in the physical infrastructure necessary for the future of AI.Nebius, which is listed in the U.S., was last seen up 11% in premarket trading. The stock is up 149% year-to-date.Stock Chart IconStock chart iconNebius shares year-to-date.Nebius has emerged as a key AI compute provider in Europe and has secured several partnerships in recent months, including a $27 billion deal with Meta in March. Nebius will provide $12 billion of dedicated capacity and up to $15 billion of additional compute capacity over five years as part of the deal. It also secured a $2 billion investment from Nvidia in the same month. The deal will see the two firms collaborate on AI infrastructure deployment, fleet management, inference and AI factory design and support.