  We studied the crystal and magnetic structure of Ca2RuO4 by different
diffraction techniques under high pressure. The observed first order phase
transition at moderate pressure (0.5 GPa) between the insulating phase and the
metallic high pressure phase is characterized by a broad region of phase
coexistence. The following structural changes are observed as function of
pressure: a) a discontinuous change of both the tilt and rotation angle of the
RuO6-Octahedra at this transition, b) a gradual decrease of the tilt angle in
the high pressure phase (p>0.5 GPa) and c) the disappearance of the tilt above
5.5GPa leading to a higher symmetry structure. By single crystal neutron
diffraction at low temperature, the ferromagnetic component of the high
pressure phase and a rearrangement of antiferromagnetic order in the low
pressure phase was observed.
