Magnetoresistance is an effect where the resistance of a material, often a metal, changes because of a magnetic field it is put in. Because magnetism and electricity are inherently liked this happens in many materials for a variety of reasons. There is also a rarer version of negative magnetoresistance where for some more unique materials a magnetic field decreases the resistance. This is a very interesting area of research and in fact the 2007 Nobel prize for physics was given to two scientists that worked on a branch of this mechanism.
In tantalum arsenide (TaAs2) it has been shown that this resistance drop is massive for relatively low strength magnetic fields. TaAs2 is a semimetal and the mechanics of the electron movement throughout it is still unknown. By using density functional theory (a way of computing electronic structures in the ground state) it was possible to prove their was no Dirac scattering (something that would require a entire new page to explain properly) in tantalum arsenide. This means it fits into no preexisting model for magnetoresistance which just means we have something new for a future Nobel laureate to discover.