  It has long remained elusive whether CuCo$_{2}$S$_{4}$ thiospinel shows bulk
superconductivity. Here we clarify the issue by studying on the samples of
sulfur-deficient CuCo$_{2}$S$_{3.7}$ and sulfurized CuCo$_{2}$S$_{4}$. The
sample CuCo$_{2}$S$_{3.7}$ has a smaller lattice constant of $a=9.454$ {\AA},
and it is not superconducting down to 1.8 K. After a full sulfurization, the
$a$ axis of the thiospinel phase increases to 9.475 {\AA}, and the thiospinel
becomes nearly stoichiometric CuCo$_{2}$S$_{4}$, although a secondary phase of
slightly Cu-doped CoS$_2$ forms. Bulk superconductivity at 4.2 K and Pauli
paramagnetism have been demonstrated for the sulfurized CuCo$_{2}$S$_{4}$ by
the measurements of electrical resistivity, magnetic susceptibility, and
specific heat.

Superconductivity;Materials Science;Strongly Correlated Electrons