Multiple mechanisms for extremely large magnetoresistance (XMR) found in many topologically nontrivial/trivial semimetals have been theoretically proposed, but experimentally it is unclear which mechanism is responsible in a particular sample. In this paper, by the combination of band structure calculations, numerical simulations of magnetoresistance (MR), Hall resistivity, and de Haas-van Alphen (dHvA) oscillation measurements, we studied the MR anisotropy of $\mathrm{Si}{\mathrm{P}}_2$ which is verified to be a topologically trivial, incomplete compensation semimetal. It was found that as magnetic field $H$ is applied along the $a$ axis, the MR exhibits an unsaturated nearly linear $H$ dependence, which was argued to arise from incomplete carriers compensation. For the $H\parallel \left[101\right]$ orientation, an unsaturated nearly quadratic $H$ dependence of MR up to $5.88\times {10}^4\%$ (at 1.8 K, 31.2 T) and field-induced up-turn behavior in resistivity were observed, which was suggested due to the existence of hole open orbits extending along the $k_x$ direction. Good agreement of the experimental results with the simulations based on the calculated Fermi surface (FS) indicates that the topology of FS plays an important role in its MR.

• Received 14 February 2020
• Revised 11 August 2020
• Accepted 31 August 2020

DOI:https://doi.org/10.1103/PhysRevB.102.115145