  The Blonder-Tinkham-Klapwijk model of the Point-Contact Andreev Reflection
spectroscopy does not provide an adequate description of experiment in the
presence of magnetic field. We demonstrate this using a junction between a
niobium tip and a copper film. We modify the the-ory to explicitly take into
account the contribution to conductance that stems from the normal vortex cores
in the superconductor. These results have important implications for
interpretation of transport spin polarisation measurements using PCAR
technique. We demonstrate that stray magnetic fields can be responsible for the
experimentally observed dependence of the spin po-larisation on the strength of
the interface barrier, and potential misassignment of the inferred spin
polarisation.
