Early starters Thomas Detry, Masahiro Kawamura and Adrian Meronk had set the target at nine under in the fourth Rolex Series event of the season and it looked for a long time like they would lead the way into the weekend but the Swedish duo had other ideas.
Söderberg recovered from an opening bogey to turn in 33 and then made a hat-trick of gains from the tenth but he was still two shots off the lead before he birdied the 17th and eagled the last to card a 64 and get to ten under.
At that point, Åberg was back on the final tee at nine under having birdied the 16th and 17th to add to five further gains and a double-bogey.
And with the light of the scoreboard illuminating the 18th green in the fading light, he holed from four feet to sign for a 66 and join his countryman at the summit.
Home hero Tommy Fleetwood then completed a birdie-birdie finish in almost total darkness to card a 66 of his own and join the group a shot off the lead.
Austria's Sepp Straka and Englishman Aaron Rai were in the clubhouse at eight under alongside Dane Marcus Helligkilde, who had four holes left to play and would be one of 24 players returning to complete their rounds on Saturday after an earlier fog delay.
Åberg, Fleetwood and Straka will be playing for Europe at the Ryder Cup in two weeks' time and all 12 members of Luke Donald's team will be in action this weekend, with Rory McIlroy birdieing the last in the dark to make the cut on the number.
Åberg's place in the team is another step in a remarkable rise for the former college superstar and Amateur World Number One who only turned professional in June.
His selection to face the United States came just a day after he claimed his first DP World Tour title in Switzerland and he will now head into the weekend in pole position for a maiden Rolex Series victory having not yet played a Major.
"I thought it was great," he said of his round. "It showed that even though I wasn't as sharp off the tee as I would want to be, I still was able to find a good score.
"Really pleased with my irons and my wedges. Felt like I gave myself a lot of chances and was striking the ball quite well. Looking forward to the next couple days, so it will be a lot of fun.
"It was a little bit nerve-wracking both yesterday and today but I'm proud of the way I handled it and looking forward to the next couple of days."
Söderberg was also a winner up the mountain in Crans-Montana in 2019 and is on target for his best finish in the Race to Dubai Rankings in Partnership with Rolex thanks to four top tens this season, including a tie for second in the opening Rolex Series event in Abu Dhabi.
"It's going to be a lot of fun," he said of the 36 holes to come. "It kind of feels like it came from nowhere.
"Struggling a little bit last week on the weekend and has not felt great at the start of this week. Just trying to find some contact with my irons and they have kind of been going everywhere. So I guess some of that work finally paying off and I'm starting to hit some quality shots.
"It's a huge tournament. The whole Ryder Cup squad is here. It's going to be a lot of pressure and I'm going to try to enjoy it as much as I can."
A poor tee-shot led to Söderberg's opening bogey but he put his tee-shot to nine feet on the par-three second to bounce back, adding gains from inside six feet at the sixth and ninth.
He was inside five feet on the tenth and 11th and made a two-putt gain on the par-five 12th before also capitalising on the two closing par-fives, getting down in two from off the green at the 17th and holing a 15-footer on the last.
His solo lead would not last long, however, as Åberg produced some late magic of his own.
A 17-footer on the second would be followed by two putts on the par-five fourth and while he hit a smart approach into the seventh, a double-bogey after tee and sand trouble on the ninth stalled his progress.
He took advantage of the 12th and then chipped in on the 14th but the best was to come as he left himself eight feet on the 16th, a tap-in on the 17th and got up and down on the last after a ragged tee-shot forced him to lay-up.
Kawamura was the star of the earlier starters as the Japanese carded a bogey-free 65, while Pole Meronk and Belgian Detry both signed for rounds of 68.
Fleetwood recovered from an opening bogey with seven birdies, including two to close, to sit a shot ahead of Straka, who carded a 66 and Rai who needed one more blow.
Ryder Cup star Tyrrell Hatton, fellow Englishman Matthew Baldwin, Spaniard Jorge Campillo, Kiwi Ryan Fox, South Korea's Tom Kim and Scot Connor Syme were at seven under.