  We have investigated the in-plane anisotropy of the c-axis magnetoresistance
for single crystals of a BiCh2-based superconductor LaO0.5F0.5BiSSe under
in-plane magnetic fields. We observed two-fold symmetry in the c-axis
magnetoresistance in the ab-plane of LaO0.5F0.5BiSSe while the crystal
possessed a tetragonal square plane with four-fold symmetry. The observed
symmetry lowering in magnetoresistance from the structural symmetry may be
related to the nematic states, which have been observed in the superconducting
states of several unconventional superconductors.
