  We measure the pressure dependence of the electrical resistivity and the
crystal structure of iron superconductor Sr2VO3FeAs. Below ~10 GPa the
structure compresses but remains undeformed, with regular FeAs4 tetrahedrons,
and a constant Tc. Beyond 10GPa, the tetrahedron strongly distorts, while Tc
goes gradually to zero. Band structure calculations of the undistorted
structure show multiple nesting features that hinder the development of an
antiferromagnetic ground state (AF), allowing the appearance of
superconductivity. The deformation of the tetrahedra that breaks band
degeneracy degrades multiple nesting, thus favouring one particular AF state at
the expense of Tc.
