Description
The superconductivity of $Sr_2RuO_4$, suspected to have a
chiral order parameter $\Delta\sim p_x\pm ip_y$, responds
sensitively to uniaxial pressure. In this talk, I will present
evidence that uniaxial pressure drives one of the Fermi
surfaces through a Van Hove singularity at a compression of
$\sim0.6\%$, and at this point the superconductivity is
dramatically strengthened: Tc passes through a pronounced
peak, at which it is more than double its zero-pressure value,
and $Hc_2$ is enhanced by more than a factor of twenty.
This very strong enhancement of $Hc_2$ suggests even-
parity pairing at this strain, meaning that there might be a
strain-induced odd-parity to even-parity transition.
