  Recently there is a great excitation about enhancement of the superconducting
transition temperature in bilayer LaSrCuO materials. Responsible for this
phenomenon is probably the interface superconductivity, predicted by Ginzburg
in 1964. The interface-superconductivity-like effects were already observed in
conventional superconductors. In 1990 we observed that the superconducting
critical temperature of both sides (interface and surface) of the high-Tc films
can be different and we have found an enhancement of the Tc if the films are
covered with silver. Our interpretation is that we observe an interface
(surface) enhanced superconductivity on the interface side by the substrate and
on the surface by the silver. In the annealed YBCO/Ag bilayers magnetic
properties of the interface were observed. Unfortunately two of our papers were
not accepted for publication and only the paper presented on SQUID 91
conference was published. Now after 19 years I would like to show some of these
old unpublished results and to point out that the observed phenomena are
probably a common feature of such layer systems.
