  Moisture-induced superconductivity was observed in FeTe0.8S0.2. With exposing
the sample to the air, the zero resistivity temperature and the superconducting
volume fraction were enhanced up to 7.2 K and 48.5 %, respectively, while the
as-grown sample showed only filamentary superconductivity. We concluded that
the causes of the evolution of superconductivity were water-related ions and/or
molecules, because only the sample kept in water at room temperature for
several days showed superconductivity. The speed of evolution of
superconductivity was strongly enhanced by immersing the sample into the hot
water.
