I have left a row (at 30cm spacing) between my early and main crop rows of taters to grow dwarf beans - I read that they are good companion plants. I have also left a row between the taters and the corns to grow rolet squash so that I can do the 3 sisters thing. The rolet squash may start sneaking into the tater rows but hopefully by that time it won't matter. And a second bonus I think, it that it will keep the weeds down.
Also a good idea is to plant horseradish (in pots) around the tater patch - also a good companion planting.
Jitterbug