  Superconductivity is achieved in Nd1-xCexOBiS2 via electron doping using
mixed-valence Ce ions. Single crystals with x = 0.2, 0.3, 0.4, and 0.5 are
generated using a CsCl flux method. Plate-like single crystals with dimensions
of 0.8 0.8 0.2 mm3 were obtained. The magnetic susceptibility chi(T) indicates
large diamagnetism, and the electrical resistivity rho(T) indicates zero
resistivity. The maximum value of Tc is observed at 4.7 K in Nd0.8Ce0.2OBiS2
from chi(T). From the rho(T) measurements taken in several magnetic fields, the
upper critical field mu0Hc2(0) is estimated to be about 12 and 0.34 T for the
ab- and c-planes, respectively. We redetermined mu0Hc2(0) of NdO0.7F0.3BiS2, as
about 35 and 0.78 T for the ab- and c-planes, respectively. The anisotropic
parameter is estimated to be about 35 for Nd0.7Ce0.3OBiS2 and 45 for
NdO0.7F0.3BiS2. The mu0Hc2(0) of Nd0.7Ce0.3OBiS2 is approximately two times
smaller than that of NdO0.7F0.3BiS2, although the difference of Gamma is
approximately 10.
