Meet Amanda Seyfried's New Boyfriend
09/15/2011 AT 02:40 PM EDT
The two have been dating "for about a month," a source tells PEOPLE. "They are calling themselves a new couple."
Tuesday night, the couple looked cozy at the Eric Trump Foundation's 5th Annual Golf Invitational & Gala at Trump National Golf Club in Westchester, N.Y., which benefited St. Jude's Children's Research Hospital. Joblon serves on the board of the Eric Trump Foundation.
An observer says he sensed "they had great chemistry" and "were great together." According to The New York Daily News, the two kept their distance during the press-heavy cocktail reception, but cozied up to one another once dinner started.
At the event, Bret Michaels performed, donated $25,000 to the foundation and asked partygoers to match it. Seyfried stepped up and matched his pledge.
Earlier this year, the actress, 25, and Ryan Phillippe were involved. Before that, she dated her Mamma Mia! costar Dominic Cooper for more than three years.
Sept. 5 she was at the U.S. Open with Franck Raharinosy, co-owner of the ping pong club SPiN New York. Seyfried said, "I'm friends with him. He's a good, smart guy."