Alexander Bjork of Sweden and Scott Jamieson of Scotland share the halfway lead on 10 under par at the Tshwane Open as a thunderstorm disrupted the second round at Pretoria County Club on Friday.
Australia's Ben Eccles, who began the day one-shot off the lead, endured a difficult round, carding a two-over-par 73 to slip to three-under and slide down the leaderboard.
Tour rookie Bjork, who was in a three-way tie for the lead after the first round, kept up his form with a four-under-par 67 which included two bogeys.
"I played well today," he said. "I had some troubles on some holes with the distance on the irons but overall it was a good round."
Jamieson added a 65, including seven birdies and a bogey, to his opening 67 for a two-round total of 132. His only previous Tour title came in South Africa in 2012.
The leaders had a one-stroke advantage over James Morrison of England, who had his round interrupted for just short of an hour because of the bad weather.
A further shot back were the home trio of Peter Karmis, Thomas Aiken and Justin Walters.
Aiken was on course for a remarkable 59 but made a bogey on his third-last hole and needed a par-save on the last after finding water to post a nine-under-par 62.
"It was there," he told reporters. "You don't get too many opportunities in your career to shoot one. I did my best to try and make a few birdies when I had the opportunity coming in, and it just didn't happen."
