The duo was in full PDA-mode at a July 4 party, Us Weekly reports in its newest issue.
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"His hand was on her butt as she was grinding into him and they were making out at the bar," a fellow attendee of the Hollywood party said. "Liam was draped all over her. It was so PDA and in-your-face!"
Liam and Maika were also spotted getting drinks together on July 7.
The two, though, are anything but official, a source said, "but their chemistry is ridiculous."
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Since splitting with fiancé Miley Cyrus in September of 2013, Liam's love life has remained largely out of the public eye, whereas Miley's has been anything but quiet. Following a high-profile romance with Patrick Schwarzenegger, Miley is now being linked to Victoria's Secret model Stella Maxwell.