  The effect of uniaxial pressure on superconductivity was examined for a
high-Tc cuprate La1.64Eu0.2Sr0.16CuO4, which is located at the boundary between
the superconducting and stripe phases. We found remarkably large anisotropy of
the uniaxial pressure effect not only between the in-plane and out-of-plane
pressures but also within the CuO2-plane. When the pressure is applied along
the tetragonal [110] direction, we found the largest pressure effect ever
observed in cuprates, dTc/dP - 2.5 K/kbar, while the change of Tc was not
appreciable when applied along [100]. This substantial in-plane anisotropy is
attributed to an intimate link between the symmetry of the one-dimensional
stripes and that of the strain produced within the CuO2 plane.
