Chasing 170 to win the first semi-final, Allen hit an unbeaten 100 off just 33 balls, to obliterate the previous mark of 47 balls by Chris Gayle, as New Zealand raced home with 7.1 overs to spare.
Allen went on a rampage as he finished with two fours, two sixes and a four off successive balls to hit the winning runs and reach his hundred with a roar of delight at Eden Gardens.
Tim Seifert hit 58 in a 117-run opening stand with Allen off just 9.1 overs to set up the victory romp.
Seifert hit two sixes and seven fours while Allen bludgeoned eight sixes and 10 fours in a brutal display of controlled power hitting.
“Obviously, we wanted to start looking straight and obviously try and put them on the back foot early,” said Allen.
“I think it’s easy for me when Timmy’s (Seifert) going like that, I can kind of just watch and then hit it when it’s in my area and just try and give him the strike.”
New Zealand, who edged into the semi-finals on net run rate but are seeking a first World Cup title, will play either India or England in Sunday’s final in Ahmedabad.
Spinners Rachin Ravindra and Cole McConchie took two wickets each to restrict South Africa to 169-8 after New Zealand elected to field first.
The 2024 runners-up South Africa, led by Aiden Markram, had been unbeaten in seven matches but slumped to 77-5 before Marco Jansen hit an unbeaten 55 to give the total some respect.
“We knew obviously how good South Africa are, and they’ve shown that throughout the tournament,” said New Zealand captain Mitchell Santner.
“So, to put on a performance like that in a crunch game is obviously pretty pleasing.”
Seifert reached his fifty off fast bowler Lungi Ngidi. Allen raised his half-century off 19 balls.
Kagiso Rababa bowled Seifert in the 10th over but it was South Africa’s only success.
Rachin Ravindra and Cole McConchie earlier took two wickets each before Tristan Stubbs (29) and Jansen put on 73 for South Africa.
Jansen hit two fours and five sixes in his 30-ball knock.
McConchie struck first in the second over with his off-spin to send back Quinton De Kock for 10 and Ryan Rickelton next ball, but Dewald Brevis avoided the hat-trick.
Left-arm spinner Ravindra had Markram caught in the deep by Daryl Mitchell for 18.
David Miller fell for six to Ravindra five balls later, with Mitchell again taking the catch at long-on.
South Africa had lost half their side in 10.2 overs when Jimmy Neesham cut short Brevis’s knock on 34.
Ferguson bowled Stubbs but Jansen hit him for six to reach his fifty.
Pace bowler Matt Henry, who arrived back only on Tuesday night after going home for the birth of his child, took 2-34.
“I think you look at conditions early and they bowled really well up front,” said Markram.
“Ball didn’t quite feel like coming on, some were just stopping on the wicket and some were hitting quite low on the bat and they made scoring really tough.” (AFP)
Edited by Cecil Wong
