The Schwaiger sisters have become a hit back home in Austria
Austria's Schwaiger sisters pulled off a stunning victory to defeat European champions Sara Goller and Laura Ludwig of Germany in the beach volleyball.
Doris and Stephanie won 23-21 11-21 18-16 to reach the last eight.
"That's the most disappointing defeat of my career," said Goller. "I'm a bit empty because you work two years for this event and then it's gone."
Reigning champions Kerri Walsh and Misty May-Treanor of the US managed a hard-earned win over Belgium.
The Americans survived five set points in the first set before beating Liesbeth Mouha and Liesbet van Breedam 24-22 21-10 in 38 minutes.
It was the 105th consecutive victory for the Americans - and marked Walsh's 30th birthday in style.
Nicole Branagh and Elain Youngs also won to keep alive the possibility of an all-American final.