Martin, the 23-year-old former Oklahoma State star who won the Alfred Dunhill on Sunday at Leopard Creek, was 11 under after two rounds at Jack Nicklaus-designed Pearl Valley. Hansen shot a 69, and Alejandro Canizares (67) was third at 5 under.
Hansen is in position to become the first player from the northern hemisphere to win the Sunshine Tour money title. A two-time winner in four tour starts, he entered the season finale with $467,823 – $173,370 more than second-place Charl Schwartzel.
Needing a victory to top the money list, Schwartzel followed his opening 77 with a 68 to make the cut by a stroke at 1 over.
The tournament also is sanctioned by the European Tour.