  Crystal structure and properties of a new member of oxy-bismuth-sulfide
SmO1-xFxBiS2 are reported here. The compounds SmO1-xFxBiS2 (x = 0.0 and 0.5)
are found to be isostructural with LaOBiS2 and crystallize in the CeOBiS2 type
structure (P4/nmm). Sm substitution in LaO0.5F0.5BiS2, (La1-ySmyO0.5F0.5BiS2),
leads to a gradual decrease in a-lattice constant however the c-lattice
constant does not show such a gradual trend. Enhancement in Tc is achieved upon
partially substituting La by smaller Sm ion. Maximum Tc ~ 4.6 K was observed
for composition with y = 0.8. Disobeying this trend Tc disappears unexpectedly
in composition SmO0.5F0.5BiS2 (y = 1.0). Both the undoped and F-doped (x = 0.0
and 0.5) compounds are paramagnetic exhibiting semiconducting behavior down to
2 K.

Superconductivity