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Bill and Melinda Gates have fun watching Roger Federer advance on Friday in Indian Wells.

Read & Watch: Federer/Gates: The Unbeaten Duo In Indian Wells

Legends in their fields have teamed up for charity

And you thought Novak Djokovic and Fabio Fognini have been playing good doubles this week at the BNP Paribas Open in Indian Wells.

Roger Federer and his occasional partner Microsoft co-founder and philanthropist Bill Gates are unbeaten as a team (2-0), as Federer noted after his quarter-final win against Poland's Hubert Hurkacz on Friday afternoon in the desert, as Gates and his wife, Melinda, watched.

Watch Hot Shot: Federer's Magic Thrills Indian Wells Crowd, Including Bill Gates

“We've had two matches, two wins so we're undefeated, feeling good,” Federer said on court.

Read More: Federer Trains Gates For Exhibition

The unbeaten duo has partnered twice, in 2017 and 2018, to raise money for Federer's self-named foundation in “Match For Africa” exhibitions. Both have taken place on the west coast of the U.S., in Seattle and San Jose.

My foundation is something that's super important to me,” Federer said last year.

The Swiss visited some of his foundation's projects last April in Zambia. It is my hope that in 10 years' time all children will have access to early childhood education in Zambia, as it is the foundation of all learning,” Federer said at the time.

Click here to read what Gates wrote about Roger being named one of TIME's 100 Most Influential last year.