Point-contact studies of high-temperature superconductor $\rm YBa_2Cu_3O_{7-δ}$

Point-contacts formed by the high-temperature superconductor $\rm YBa_2Cu_3O_{7-\delta}$ prepared by cryochemical technique, and a noble metal Ag or Cu) are investigated. The maximum value of the energy gap $\Delta\simeq 40~meV$ and the ratio $2\Delta/kT_c\simeq 12$ are obtained. It is found that along certain crystallographic axes of the superconductor under investigation, the electrical resistivity $\lesssim 10^{-5} \Omega\cdot cm$.