Joaquin Niemann broke the 36-hole tournament record to take a two-shot lead into the weekend at the Genesis Invitational, where Justin Thomas also impressed.
Niemann, without a PGA Tour victory since 2019, fired his second successive 63 at Riviera Country Club to move to 16 under and two shots clear of Cameron Young.
Thomas is five off the halfway lead in third after bogey-free 64, with former world No 1's Adam Smith and Jordan Spieth in a share of fourth place after Collin Morikawa.
The highlight of Thomas' round was a 30-foot eagle at the par-five 11th, having also birdied three of his opening six holes, with back-to-back gains from the 16th taking him to 11 under.
"Shooting 11 under, I would have thought that I would probably be leading, not five back," Thomas said. "There's still a lot of golf left. I think the reason you see the scores, such disparity in them is because of how firm it is."
Scotland's Russell Knox leads the British interest and sits in tied-seventh on seven under with Norway's Viktor Hovland and Australia's Cameron Smith, while Rory McIlroy is in the group on three under after mixing two birdies with a lone bogey in a second-round 70.
World No 1 Jon Rahm, FedExCup winner Patrick Cantlay and Masters champion were among the notable names to make the cut on the number at even par, while former Riviera winners Dustin Johnson, Bubba Watson and Patrick Reed all made an early exit.
Niemann's record-breaking start
The Chilean started his round with a close-range eagle after a brilliant approach into the par-five first, with Niemann rolling in from 15 feet at the second and adding further birdies at the seventh and ninth to reach the turn in 30.
Niemann cancelled out a lone bogey at the 10th by picking up a shot at the next and then holing a 42-foot at the 12th, before converting from 20 feet at the 14th and moving further of Young by posting a two-putt birdie on his penultimate hole.
"It feels like forever actually [since his last win]," Niemann said. "Obviously you play this game to try to win every week and yeah, but you know how hard it is to win here and how competitive they are, how many good players there are here. You have to be patient and just wait for my week."
Niemann broke the 36-hole record set around 30 minutes earlier by Young, who fired nine birdies on a blemish-free card - including on each of his last four holes - to post a round-of-the-day 62.
Watch the Genesis Invitational throughout the weekend live on Sky Sports. Live coverage continues on Saturday from 5pm on Sky Sports Golf.