The 21-year-old from Dalarna had a boom in the second shooter and finished two minutes from the podium.
Before that, Elisabeth Högberg and Anna Magnusson placed tenth in thirteenth place.
Two Swedes with world cup merits.
During the season, Halvarsson has made his debut in the IBU Cup and taken several fine placements.
Both today's winner Monika Hojnisz-Starega, Poland and runner-up Anastasiya Murkushyna, Ukraine have World Cup medals in their respective prize cabinets.
Only six Swedes got a starting place in the distance, the seventh was Stina Nilsson who instead has to put all the gunpowder on the sprint on Friday.
SVT broadcasts Saturday's hunt start.