N-S boundary resistance determined by gliding electrons, and s-shaped current-voltage characteristic

It is shown that there are physical situations when electrons ''gliding'' along the N-S boundary cause its prominent electrical resistance. In such cases, the normal-superconducting transition of a certain part of specimen is accompanied by an increase in the total electrical resistance, and the current-voltage characteristic is of the S-shape. The measurements of the effect permit the superconducting gap to be estimated directly, the latter being of practical use in determining the parameters of high-temperature superconductors