  We revealed that the superconducting transition temperature Tc of the
multi-component superconductor Sr2RuO4 is enhanced to 3.3 K under in-plane
uniaxial pressure that reduces the tetragonal crystal symmetry. This result
suggests that new superconducting phases with a one-component order parameter
are induced. We have also clarified the inplane pressure direction dependence
of the emergence of this higher-Tc superconducting phase: pressure along the
[100] direction is more favorable than pressure along the [110] direction. This
result is probably closely related to the direct shortening of the in-plane
Ru-O bond length along the pressure direction and the approach of the gamma
Fermi surface to the van Hove singularity under the pressure parallel to the
[100] direction.
