  Rare-earth monopnictides display rich physical behaviors, featuring most
notably spin and orbital orders in their ground state. Here, we grow ErBi
single crystal and study its magnetic, thermal and electrical properties. An
analysis of the magnetic entropy and magnetization indicates that the weak
magnetic anisotropy in ErBi possibly derives from the mixing effect, namely the
anisotropic ground state of Er3+ (4f11) mingles with the isotropic excited
state through exchange interaction. At low temperature, an extremely large
magnetoresistance (~104%) with a parabolic magnetic-field dependence is
observed, which can be ascribed to the nearly perfect electron-hole
compensation and ultrahigh carrier mobility. When the magnetic field is rotated
in the ab (ac) plane and the current flows in the b axis, the angular
magnetoresistance in ErBi shows a twofold (fourfold) symmetry. Similar case has
been observed in LaBi where the anisotropic Fermi surface dominates the
low-temperature transport. Our theoretical calculation suggests that near the
Fermi level ErBi shares similarity with LaBi in the electronic band structures.
These findings indicate that the angular magnetoresistance of ErBi could be
mainly determined by its anisotropic Fermi surface topology. Besides,
contributions from several other possibilities, including the spin-dependent
scattering, spin-orbit scattering, and demagnetization correlation to the
angular magnetoresistance of ErBi are also discussed.
