Sterne rode a 10-under-par 62 to the first-round lead but his second round was a more sedate 2-under 70. He's at 12-under 132 halfway through the tournament.
Thorbjorn Olesen, for the second time in the tournament, had a string of four consecutive birdies en route to a 6-under 66 and Tommy Fleetwood shot a bogey-free 68 and Stephen Gallacher, who again had back-to-back bogeys, had a 70 in creating a three-way tie for second. They are at 11-under, one stroke back of Sterne.
Chris Doak (69 Friday), Andreas Harto (67) and Maximilian Kieffer (68) are tied for fifth at 12-under 134.
Sterne opened his second round with a birdie but had his first bogey of the tournament at the No. 4. He also bogeyed the 14th hole but dropped in birdies on all three of the par 5s on the second nine. His 4 at the 564-yard 18th pulled him ahead of Olesen, Fleetwood and Gallacher.
Olesen, who had birdies over Nos. 4-7 Thursday, matched that run with birdies over 10-13 in the second round.
Gallacher had bogeys at the 12th and 14h holes, where he went birdie-eagle in the first round.