Antimatter Blues by Edward Ashton

Edward Ashton's Antimatter Blues is the thrilling follow up to Mickey7 in which an expendable heads out to explore new terrain for human habitation.
Summer has come to Niflheim. The lichens are growing, the six-winged bat-things are chirping, and much to his own surprise, Mickey Barnes is still alive—that last part thanks almost entirely to the fact that Commander Marshall believes that the colony's creeper neighbors are holding an antimatter bomb, and that Mickey is the only one who's keeping them from using it. Mickey's just another colonist now. Instead of cleaning out the reactor core, he spends his time these days cleaning out the rabbit hutches. It's not a bad life.
It's not going to last.
It may be sunny now, but winter is coming. The antimatter that fuels the colony is running low, and Marshall wants his bomb back. If Mickey agrees to retrieve it, he'll be giving up the only thing that's kept his head off of the chopping block. If he...