We succeed in enhancement of a superconducting transition temperature (T c ) for NdO 0.7 F 0.3 BiS 2 single crystal by partial substitution of Pb for Bi. The T c increases with increasing Pb concentration until 6%. The maximum T c zero is 5.6 K, which is the highest value among BiS 2 based superconductors synthesized under an ambient pressure. Pb substitution forBi induces lattice shrinkage along the c axis. These results reflect that superconductivity in this system is responsive to the lattice strain.

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Antimony (Sb) substitution of less than 8% was examined on a single crystal of a layered superconductor NdO 0.7 F 0.3 BiS 2 . The superconducting transition temperature of the substituted samples decreased as Sb concentration increased. A lattice constant along the c-axis showed a large decrease compared with that along the a-axis. Since in-plane chemical pressure monotonically decreased as Sb concentration increased, the suppression of the superconductivity is attributed to the decrease in the in-plane chemical pressure.

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