Residual critical current in high T_c bicrystal grain boundary junctions

We have recently reported on the persistence of a significant zero voltage current across bicrystal grain boundary junctions of YBa2Cu 3O7-δ in an external magnetic field of several Tesla. In this note we present data on the dependence of this residual current on temperature and orientation of the grain boundary. A description of the grain boundary as being comprised of superconducting microbridges separated by normal regions is consistent with the experimental data.