Extremely large magnetoresistance in an unfilled skutterudite quadratic contact point semimetal CoP₃

Extremely large magnetoresistance (EXMR) and high mobility are always desired for use in spintronic devices. Herein, we report the observation of EXMR and very large hole mobility reaching similar to 2 x 10(4)% (30 T) and similar to 2 x 10(4) cm(2) V-1 s(-1), respectively, at 2 K in an unfilled skutterudite CoP3 crystal. The magnetotransport measurements unveil remarkable Shubnikov-de Haas quantum oscillations hosting nontrivial Berry phase induced by strong Zeeman splitting. First-principles calculations suggest band inversion between Co-d(xy)/(yz) and P-p(z) orbitals, which forms fourfold quadratic contact point at the C point above the Fermi level of similar to 0.146 eV. The angle-resolved photoelectron spectroscopy measurements verify the calculated surface state. The results provide a quadratic contact point semimetal, which has potential applications in topological devices.