Intergrain ordering of a superconductive ceramic of YBa2Cu4O8 at zero external magnetic field studied by linear and nonlinear transport coefficients

The intergrain ordering in a superconductive ceramic of YBa2Cu4O8 at zero e xternal magnetic field is investigated hy AC resistivity measurements. The third harmonic in-phase voltage component V-3 omega' to a weak AC current s hows a distinct negative peak across the intergrain transition temperature T-C2, but not across the intragrain one T-C1 (T-C2 < T-C1). A divergence of the nonlinear resistivity rho(2) is concluded at T-C2 in the limit of vani shing AC current, while the linear resistivity po remains finite even at an d below T-C2. Such characteristic critical behaviors of the intergrain orde ring of the present superconductive ceramic strongly suggest a chiral glass ordering recently predicted to occur in high-T-C superconductive ceramics.