Read & Watch: Ymer Pleases Home Crowd In Stockholm
Ymer broke when Marterer tried to serve it out at 5-4 in the third. And on match point, with Marterer serving at 5-6, the German served and volleyed and hit a backhand volley into the open court. But Ymer ran it down, and on the dead run, clipped a forehand down the line for the win.
The 22-year-old Swede will next meet fourth seed and two-time finalist Jack Sock of the U.S. In the only other main-draw match of the day, American Denis Kudla beat Guillermo Garcia-Lopez of Spain 6-2, 7-5. Kudla will next meet South Korea's Hyeon Chung or countryman Taylor Fritz.
Watch: Ymer Visits Ethiopia