  The interaction between planar quasiparticles in a dx2-y2 superconductor and
quantized vortices associated with a magnetic field perpendicular to the plane
is shown to induce a pair potential with dxy symmetry, out a phase with dx2-y2
order. A microscopic calculation of a process involving quasiparticle
scattering by the supercurrent around a vortex and Andreev reflection from its
core is presented. Other processes also leading to an idxy pair potential are
discussed. It is argued that such a fully gapped state may be the high field
low temperature phase observed by Krishana, Ong et al in magnetothermal
conductivity measurements of superconducting single crystal {\em Bi} - 2212.
