  We report measurements of the thermoelectric power and electrical resistivity
of superlattices composed of the high-temperature superconductor
YBa2Cu3O(7-delta) (YBCO) and the metallic ferromagnet La(2/3)Ca(1/3)MnO3 (LCMO)
with individual layer thicknesses between 5 and 50 nm. Whereas YBCO and LCMO
reference films prepared under the same conditions exhibit negative Seebeck
coefficients, in excellent agreement with data on bulk compounds of identical
composition, those of all superlattices are positive, regardless of the
individual layer thickness. Having ruled out lattice strain and incomplete
oxygenation, we attribute the observed sign reversal of the Seebeck coefficient
to a long-range electronic reconstruction nucleated at the YBCO-LCMO
interfaces.
