The Polish-American duo on Sunday defeated top-seeded pair Hsieh Su-wei of Taiwan and Belgium’s Elise Mertens 5-7, 6-4, 7-5.
Świątek and Mattek-Sands next take on the winners of a match pitting Taiwan’s Chan Hao-ching and Latisha Chan against Croatia’s Darija Jurak and Slovenia’s Andreja Klepač.
Twenty-year-old Świątek, who is defending her women's singles title in Paris, defeated Estonia’s Anett Kontaveit 7-6, 6-0 in the third round on Saturday.
On Monday she plays Ukraine's Marta Kostiuk for a place in the singles quarterfinals.
Świątek won last year's French Open to claim her maiden Grand Slam title, and became the first Pole to lift a Grand Slam singles trophy.
(pk)
Source: PAP