  We report detailed transport studies on ferromagnet-superconductor
heterostructures. Epitaxial heterostructures of half-metal colossal
magnetoresistive La2/3Ca1/3MnO3 (HM-CMR) and high Tc superconducting YBa2Cu3O7
(YBCO) are grown on SrTiO3 (100) single crystal substrates by pulsed laser
deposition. Using the HM--CMR layer as source for spin-polarized
quasiparticles, we show the effect of injection of spin-polarized
quasiparticles into the ab-plane and along the c-axis of YBCO. The results show
a drop in the ab-plane resistance Rab (T) in the case of injection along the
c-axis that is discussed to be related to the opening of a pseudogap.
