looking for title with logical first officer

[Violaguy]

I am trying to remember the name of a book I read long ago, probably from the 70s. It was a bit of a Star Trek knockoff, future with space travel and alien civilizations, but what I remember particularly was the hyperlogical first/science officer, fairly spock-like. He dies at the end and some kind-hearted alien is 'so sad'. There was some romantic interest also, sacrificed for duty. Hope that's enough to jog someone's memory! Maybe his name was Mrek or something like that, just maybe. Thanks!