Sources tell TMZ Cardi recently stepped into the studio with none other than Meek Mill to lay down some material that'll be used in a forthcoming song. We're told they cranked out hooks and verses -- all of which is fair game for a final product that's yet to be released.

Unclear on who the featured artist would be, but we do know that Meek's got an album in the works right now. Sources also say the content Cardi and Meek recorded has the potential to be a huge hit ... so, clearly, expectations are high.

Adding insult to injury, the new duo were seen being friendly last week at the Billboard 2018 R&B Hip-Hop Power Players party in NYC ... where Meek was given the Impact Award.

While we're told the collab happened a few months ago, the timing is nothing short of less-than-perfect for Nicki ... who's in the middle of a good ol' fashioned beef with Cardi.

Their NYFW fight earlier this month left Cardi with a fat lump on her eye ... and a lot of ill will between the two. That hasn't prevented them from being in the same vicinity though since then.