  We have successfully synthesized a new superconducting phase of FeTe1-xSx
with a PbO-type structure. It has the simplest crystal structure in iron-based
superconductors. Superconducting transition temperature is about 10 K at x =
0.2. The upper critical field Hc2 was estimated to be ~70 T. The coherent
length was calculated to be ~2.2 nm. Because FeTe1-xSx is composed of nontoxic
elements, this material is a candidate for applications and will activate more
and more research on iron-based superconductor.
