Adrien Saddier set a new course record to join Chris Paisley in a four-shot lead at the top of the SA Open leaderboard on Friday.
Frenchman Saddier produced a fine birdie-eagle-birdie finish to sign for a brilliant and unprecedented nine-under 63 at the Glendower Golf Club.
The 25-year-old, looking for his first victory on the European Tour, is yet to drop a shot through 36 holes, while a bogey at the 13th cost Paisley outright ownership of top spot.
The Englishman birdied four of his last five holes to streak clear before being caught by Saddier, while Jacques Kruyswijk moved into third.
Kruyswijk only earned his place on the Tour through qualifying school in November and posted four gains to keep himself in the hunt for glory on home soil in Gauteng.
Overnight leaders Branden Grace and Chase Koepka fell down to a four-way share for fourth after carding one-under 71s, the latter producing an inconsistent round that included four bogeys.
Defending champion Graeme Storm paid for a poor opening round by missing the cut despite a two-under 70 in his second outing, but host Ernie Els will feature at the weekend.