Rory McIlroy reached the Dubai Desert Classic halfway point in a share of the lead with Denmark's Thomas Bjorn.
The world number two from Northern Ireland added a sublime 65 to his opening 66 to finish on 13 under par.
But 40-year-old Bjorn, who beat Tiger Woods to triumph in 2001, then matched McIlroy's round and total.
Overnight leader Rafael Cabrera-Bello is one back after a 69, while world number four Martin Kaymer is 12 under and England's Lee Westwood is 10 under.
"Another great day in Dubai! Exciting weekend ahead," McIlroy said afterwards on Twitter.
McIlroy, who won his first professional title on the course three years ago, began the day three shots behind Cabrera-Bello.
But he heaped pressure on the Spaniard straight from his start on the 10th tee with five birdies in his opening six holes.
He turned in a four-under 33, despite missing an eagle chance of less than 10 feet at the long 18th for the second day running.
Kaymer also started on the back half. The highlight of his 67 was an ace on the 186-yard seventh for the first hole-in-one of his professional career.
It hauled the German, who had drawn level with McIlroy after a birdie on the second, back to one shot behind the leader.
Denmark's Bjorn has given himself another chance of lifting the trophy that he won with a tournament record score in 2001.
He put himself alongside McIlroy at the halfway stage with five birdies on the way back to the clubhouse.
Westwood shares seventh place with Kaymer's compatriot Marcel Siem and Scot Stephen Gallacher, who shot 65 a day after holing in one at the 15th.
Another Briton Scott Jamieson, who started day two in joint second, carded 68 to remain two shots off the pace.