  X-ray diffraction (XRD) experiments have been carried out on quartz-like
GaPO4 at high pressure and room temperature. A transition to a high pressure
disordered crystalline form occurs at 13.5 GPa. Slight heating using a YAG
infrared laser was applied at 17 GPa in order to crystallize the phase in its
stability field. The structure of this phase is orthorhombic with space group
Cmcm. The cell parameters at the pressure of transition are a=7.306 A, b=5.887
A and c=5.124 A.
