In this puper, we report the synthesis of a new metastable phase La4Au by means of high pressure high temperature treatment of an amorphous alloy. As starting material, the La80Au20 amorphous ribbons were prepared from melt by rapid quenching method. Synthesis conditions were found to be at about 80kbar and 250℃. This new phase has a orthorhombic structure with lattice parameters a = 6.54?, b = 7.71? and c=11.32?, and exhibits superconducting transition at Tc=5.5 K which is higher than that of any known La-Au phases.