What happened

Shares of electric-vehicle (EV) start-up Rivian Automotive (RIVN 1.23%) spiked 10% early Monday morning after a filing showed one well-known billionaire investor made a large investment in the company in the fourth quarter of 2021. As of 10:53 a.m. ET, Rivian shares pulled back slightly, but remained 8.4% above Friday's closing price. 

So what

A 13-F filing by Soros Fund Management, the investment fund run by billionaire-investor George Soros, disclosed a nearly 20 million share stake in Rivian as of Dec. 31, 2021. The investment was worth over $2 billion as of the end of the filing period. But a subsequent drop in Rivian shares means the billionaire's investment has lost over $800 million in value to date.

Blue Rivian R1S electric SUV in front of charger in a park.

Image source: Rivian Automotive.

Now what

Soros' investment is likely meant for the long term, though investors won't know its status until the investment fund next reports its quarterly holdings. But today, some investors are following the famous-investor's lead and buying in at a discount to where Soros bought shares. 

Rivian also has other large investors, including Ford Motor and Amazon. Both of those companies were backers of Rivian prior to its initial public offering (IPO) last fall.

Ford initially planned to partner with the EV start-up as the automotive giant worked to electrify its vehicle offerings. It has subsequently proceeded on its own, ending plans to co-develop vehicles with Rivian. But Amazon still has a working business relationship with the company, having ordered up to 100,000 electric-delivery vans for its last-mile e-commerce needs. 

Today's pop in shares shows that some investors are feeling bolstered by the disclosure of another major investor having a stake in Rivian. With shares down about 40% year to date, investors may feel they're getting a discount, which is helping the stock move up today.