This explosive device uses a tiny dimensional flux generator which allows anti-matter to seep through a tiny dimensional warp. The resultant explosion is very powerful. From: Apocalypse Ufopaedia
Note: although it is called a "mine", it is only an explosive device and does not have any proximity function.
A powerful Alien explosive grenade which may cause extensive damage to structures, kill grouped entities, can make a hole in the roof of a UFO, destroy large sections of cover, produce craters in terrain etc. and is able to destroy the 'orange pad' terrain features found inside buildings within the alien dimension.