Evidence of a s-Wave Pairing in Heavily Zn-doped $YB{a}_{2}C{u}_3{O}_{7-\delta }$ from Andreev Reflection Spectra

When the $d_{x^2-y^2}$-wave pairing is suppressed by Zn-doping in $YB{a}_{2}C{u}_3{O}_{7-\delta }$ some of the Andreev reflection spectra were found to be similar to the s-wave spectra of conventional superconductors. The energy gap is rather reproducible (2.3-3.0meV). It is suppressed by low magnetic field ($H_C^{PC}=120-270mT$) in great contrast to the d-wave spectra ($H_C^{PC}>3T$) with the similar order of the gap value. We suppose that the s-wave pairing occurs near the Zn-impurities.