Andy Murray and Heather Watson through, Jamie Murray and Johanna Konta fall at first hurdle
Andy Murray and Heather Watson progressed to the quarter-final stage of the mixed doubles but Jamie Murray and Johanna Konta fell at the first hurdle.
The British pair overcame David Ferrer and Carla Suarez Navarro 6-3 6-3 in one hour and six minutes.
Murray and Watson were late call ups after Romanian pair of Monica Niculescu and Florin Mergea withdrew and will now face India on Friday.
Britain's Andy Murray (R) and Britain's Heather Watson celebrate a point against Spain's Carla Suarez and Spain's David Ferrer during their men's doubles semi-final tennis match at the Olympic Tennis Centre of the Rio 2016 Olympic Games in Rio de JaneiroAFP
However, another British pair, Jamie Murray and Johanna Konta were beaten by American duo Jack and Bethanie Mattek-Sands 6-4 6-3.
Murray and Konta rarely threatened in a contest that lasted one hour and 17 minutes, with a solitary break of serve in each set enough for Sock and Mattek-Sands to secure their progression.