The Black Caps suffered their first loss in the campaign after they posted 175 for seven, as South African Marco Jansen took four wickets.
In response, opener Markram hit four sixes and eight boundaries in his unbeaten knock of 86 off 44 balls, the highest by a South African captain in the tournament’s history, helping his team reach 178 for three with 17 balls to spare.
"Wickets in the power play is always key," Black Caps captain Mitch Santner said.
"The way they put us under pressure with the ball at the start ... we were always kind of one wicket down too many at each stage.
"We were probably a little bit below par [with the bat] but the wicket was a little bit sticky, a little bit spinny.
"A better power play with the ball and we could have been right in it."
After losing the toss, the Black Caps found themselves batting first, and they found the going tough, as player of the match Jansen (four for 40) dismissed most of the top order by the seventh over.
Finn Allen (31 off 17 balls) tried to mitigate the damage after Tim Seifert and Rachin Ravindra fell to Jansen. But Jansen got Allen caught at mid off in the sixth over, leaving New Zealand struggling at 58 for three.
Mark Chapman (48) and Daryl Mitchell (32) turned things around with a 74-run partnership for the fifth wicket, until Jansen got Chapman caught by Ryan Rickelton at backward point in the 14th.
New Zealand scored only 17 runs in the next four overs, until James Neesham’s unbeaten 23 off 15 balls got them to a fighting total.
Chasing 176, South Africa got off to a fast start with Markram hitting three sixes and five boundaries to steer his team to 62 without loss in four overs.
Losing fellow opener Quinton de Kock (20) did not affect Markram, who hit Santner for a six down long on to reach his half-century in just 19 balls. By the time Rickelton (21) fell in the eighth over, South Africa had already crossed the 100-run mark.
With the required run rate falling below six, Markram did not hit a single boundary in the next seven overs, and focused on rotating the strike, getting South Africa within 28 runs of victory with 30 balls left.
David Miller, who scored an unbeaten 24, cleared the midwicket boundary to bring up the winning runs.
South Africa will conclude their group campaign against the United Arab Emirates on Wednesday, a day after New Zealand play Canada.
England beat Scotland by five wickets to move up to second in group C behind the West Indies, thanks to Tom Banton’s unbeaten half-century at Eden Gardens.
Chasing 153 for victory, Banton’s 63 off 41 deliveries guided England over the line after Scotland made early inroads into their top order.
Lorcan Tucker smashed an unbeaten 94 off 51 balls to power Ireland to a 96-run win over Oman, and the United States beat the Netherlands by 93 runs. — Reuters/Allied Media
NEW ZEALAND
T Seifert c de Kock b Jansen 13 (9)
F Allen c Markram b Jansen 31 (17)
R Ravindra c Miller b Jansen 13 (8)
G Phillips b Maharaj 1 (3)
M Chapman c Rickelton b Jansen 48 (26)
D Mitchell c Stubbs b Ngidi 32 (24)
M Santner c Rickelton b Bosch 4 (10)
J Neesham not out 23 (15)
M Henry not out 9 (8)
Extras (1lb) 1
Total (for 7wkts, 20 overs) 175
Fall: 1-33, 2-57, 3-58, 4-64, 5-138, 6-141, 7-145.
Bowling: L Ngidi 4-0-34-1, K Rabada 4-0-27-0, M Jansen 4-0-40-4, K Maharaj 3-0-24-1, C Bosch 4-0-34-1, A Markram 1-0-15-0.
SOUTH AFRICA
A Markram not out 86 (44)
Q de Kock b Ferguson 20 (14)
R Rickelton c Mitchell b Neesham 21 (11)
D Brevis c Mitchell b Ravindra 21 (17)
D Miller not out 24 (17)
Extras (6w) 6
Total (for 3wkts, 17.1 overs) 178
Fall: 1-62, 2-102, 3-131.
Bowling: M Henry 4-0-38-0, L Ferguson 3.1-0-33-1 (2w), J Duffy 3-0-50-0 (2w), M Santner 4-0-33-0 (2w), J Neesham 2-0-15-1, R Ravindra 1-0-9-1.
Result: South Africa won by seven wickets.
