  Superconducting transition temperatures Tc of the YBCO film surface and of
the YBCO film/substrate interface were measured inductively. It was observed
that the interface- Tc is always higher then the surface - Tc. However
deposition of silver over-layer enhances the superconducting transition
temperatures. This observation was confirmed by four-point resistance
measurements. In the annealed YBCO/Ag bilayers magnetic properties of the
interface were observed. We believe that such phenomena are a common feature of
layered systems. This two dimensional structure reminds the layered
microstructure of the high-temperature superconductors and one can suppose that
covering of the superconducting layer by non-superconducting layer is a
condition for obtaining high critical temperatures in general.
