IMMA PHASE OF GERMANIUM AT SIMILAR-TO-80 GPA

Ge has been studied to 81 GPa with angle-dispersive diffraction techni ques, using an image-plate area detector and high-brilliance synchrotr on radiation from the European Synchrotron Radiation Facility. A previ ously unknown phase of Ge, with orthorhombic symmetry Imma, is found t o exist above similar to 75 GPa-between the well established beta-tin and simple hexagonal phases. This phase is the same as that found rece ntly between the beta-tin and simple hexagonal phases of Si.