  We investigate the superconducting properties and possible nematic
superconductivity of self-doped BiCh2-based (Ch: S, Se) superconductor
CeOBiS1.7Se0.3 through the measurements of in-plane anisotropy of
magnetoresistance. Single crystals of CeOBiS1.7Se0.3 were grown using a flux
method. Single-crystal structural analysis revealed that the crystal structure
at room temperature is tetragonal (P4/nmm). Bulk superconductivity with a
transition temperature of 3.3 K was observed through electrical resistivity and
magnetization measurements. Investigation of anisotropy of upper critical field
suggested relatively low anisotropy in the crystal as compared to other
BiCh2-based superconductors. In the superconducting states of CeOBiS1.7Se0.3,
two-fold symmetric in-plane anisotropy of magnetoresistance was observed, which
indicates the in-plane rotational symmetry breaking in the tetragonal structure
and hence the possibility of nematic superconductivity in CeOBiS1.7Se0.3.
