Field-Induced Metal–Insulator Transition in \beta-EuP_3

Metal–insulator transition (MIT) is one of the most conspicuous phenomena in correlated electron systems. However such a transition has rarely been induced by an external magnetic field as the field scale is normally too small compared with the charge gap. We present the observation of a magnetic-field-driven MIT in a magnetic semiconductor \beta -EuP_3. Concomitantly, we find a colossal magnetoresistance in an extreme way: the resistance drops billionfold at 2 K in a magnetic field less than 3 T. We ascribe this striking MIT as a field-driven transition from an antiferromagnetic and paramagnetic insulator to a spin-polarized topological semimetal, in which the spin configuration of Eu^2+ cations and spin-orbital coupling play a crucial role. As a phosphorene-bearing compound whose electrical properties can be controlled by the application of field, \beta -EuP_3 may serve as a tantalizing material in the basic research and even future electronics.