CHAIN SCENARIO FOR JOSEPHSON TUNNELING WITH PI-SHIFT IN YBA2CU3O7

We point out that all current Josephson-junction experiments probing d irectly the symmetry of the superconducting state in YBa(2)Cu3O(7) can be interpreted in terms of the bilayer antiferromagnetic spin fluctua tion model, which renders the superconducting state with the order par ameters of extended s symmetry, but with the opposite signs in the bon ding and antibonding Cu-O plane bands. The essential part of our inter pretation includes the Cu-O chain band which would have the order para meter of the same sign as antibonding plane band. We show that in this case net Josephson currents along and perpendicular to the chains hav e a phase shift equal to pi.