How to get him to stop?

How do I get a new coworker to stop coming to my desk to talk to me, in a professional way? Pretty sure he likes me, he’s objectively “my type”, but I’m in a (rocky) 5-year relationship and need this guy at work to stop coming to my desk so I don’t cloud my judgement with my current relationship.

I am a sitting duck when he comes over. I never go over to him. How do I give him a hint??