They achieved the feat during a 12-3 win over Japan in yesterday afternoon's seventh session of round-robin play.
The British team were in charge from the start, scoring two points in the first end when Japan's skip Ayumi Ogasawara wrecked with her last stone, leaving Muirhead with a simple hit. Japan managed to score two in the second end before Muirhead had a nose-hot for another two in the third. In the fourth end Ogasawara was facing three British counters when her tap-out was weak, giving up a steal of one. Japan did manage a single score in the fifth end, to give Britain a 5-3 half-time lead. Muirhead played a nice tap out to score two in the sixth end.
In the seventh, Ogasawara was facing five British stones with her last. She wrecked on the front stone in this collection to give Muirhead her record-breaking five-point steal.
After losing two of her first three games, the Scot now shares third place with China, behind leaders Canada and Sweden.
Muirhead said: "We felt the momentum was starting to build yesterday and we continued that today. I'm happy with the way we played. We're enjoying ourselves and we're relaxed. The girls are playing fantastic, they're setting me up and it's a good team performance."
David Hay, the team coach, said: "The next four games are going to be big but Eve's pulling off all the big shots and the girls are playing well."
The women play twice today, against Korea this morning and Switzerland in the evening session.
Later, the British men kept their winning streak going against Denmark despite being 5-1 down going into the fifth-end break. A game-turning three in the sixth end and single steals in each of the ninth and 10th ends gave David Murdoch's team an 8-6 victory that put them into joint top place in the rankings alongside China and Sweden.
The team played arguably their best end of the competition so far to give Murdoch a simple draw for three shots in the sixth, reducing the gap to 5-4 in Denmark's favour. A further two points in the eighth end brought Britain level at 6-6.
Strong play by his team and strong decision-making by Murdoch piled the pressure on the Danish skip, Rasmus Stjerne, in the last two ends, forcing mistakes with his last stones in each to give Britain single steals and an 8-6 win.
Murdoch said: "I haven't come out of a game of curling with an adrenalin rush like that for a long time, not since we won the World Championships in 2009. It was outrageous out there, the noise, the ice changing, the way the game was, the huge momentum swing after that sixth end.
"We decided we'd throw the kitchen sink at them. We were really pumped for that sixth end. We were going to have to take some risks and we got that big three and it completely changed the game."
Asked if it was a fortunate win, Murdoch, whose team face Canada today, said: "When you see the amount of pressure we forced at the end, there was no luck in it, just sheer determination. I'm really proud of those guys and we really believe in ourselves. If we can just keep that confidence and start games well then we're dangerous out there."