  This article reports the experimentally clarified crystal structure of a
recently discovered sulfur hydride in high temperature superconducting phase
which has the highest critical temperature Tc over 200 K which has been ever
reported. For understanding the mechanism of the high superconductivity, the
information of its crystal structure is very essential. Herein we have carried
out the simultaneous measurements electrical resistance and synchrotron x-ray
diffraction under high pressure, and clearly revealed that the hydrogen
sulfide, H2S, decomposes to H3S and its crystal structure has body-centered
cubic symmetry in the superconducting phase.
