Observation of a spin gap in the normal state of superconducting Mo3Sb7

Magnetization, specific heat, and electrical resistivity measurements have been performed on the superconductor Mo(3)Sb(7). Two kinds of transitions are observed at 2.3 and 50 K, respectively. The former is superconducting transition, while the latter is attributed to spin-gap formation. From the analysis of the experimental data, excitation gap, intra- and interdimer interactions are estimated as Delta/k(b) approximately 120 K, J(0)/k(B) approximately 150 K, and J(1)/k(B) approximately 55 K. The electronic structure calculations using the LSDA approximation show nesting property in the Fermi surface, favoring the superconductivity.