Dix was a Human baseball player in 1957 on a team with Thompson.
In one game broadcast on the radio, and overheard by Mestral and T'Mir in Carbon Creek, Dix hit a scorcher down the right field line, past the first baseman. It was fielded by Ellis who threw Thompson out at home plate, despite a collision with the catcher, Wilcox. (ENT: "Carbon Creek")
This character was only mentioned in dialogue.
Since "Carbon Creek" takes place in October 1957, the only possible baseball game on the radio that month (after the end of the professional season) would have been a World Series game; the 1957 World Series was contested by the New York Yankees and Milwaukee Braves. In real-life, neither team had anybody named Wilcox, Ellis, or Dix on their roster (though "Thompson" may be the Braves' Bobby Thomson).