Sigfridsson's club scored five points in the second end in Draw 9 on Thursday on the way to an 8-2 victory over Ottawa's Rachel Homan.
The Swedish rink now sits in sole possession of first place in the women's standing with a 4-0 record. Mirjam Ott of Switzerland is second at 3-1 but was idle for the ninth draw. Homan is 1-2.
Edmonton's Heather Nedohin downed Japan's Satsuki Fujisawa 5-2 to improve her record to 2-1. Fujisawa's rink is 0-3 after the loss.
Saskatoon's Stefanie Lawton dispatched Latvia's Evita Regza 6-2. Lawton has a 2-1 record, while Regza drops to 0-3.
In men's play, Scotland's David Murdoch scored two points in the eighth end to slip past Switzerland's Sven Michel 6-5.
Denmark's Rasmus Stjerne earned two points in the second end to top New Zealand's Peter De Boer 5-3.
Glenn Howard of Coldwater, Ont., is still in first in the men's standings with a 3-0 record.
Murdoch, Michel, Stjerne and four other teams have 2-1 records. De Boer is 0-3.