  A huge enhancement of the superconducting transition temperature Tc was
observed in tetragonal FeSe superconductor under high pressure. The onset
temperature became as high as 27 K at 1.48 GPa and the pressure coefficient
showed a huge value of 9.1 K/GPa. The upper critical field Hc2 was estimated to
be ~ 72 T at 1.48 GPa. Because of the high Hc2, FeSe system may be a candidate
for application as superconducting wire rods. Moreover, the investigation of
superconductivity on simple structured FeSe may provide important clues to the
mechanism of superconductivity in iron-based superconductors.
