Gold contacts on superconducting crystals of YBa2Cu3O7 with very low contact resistivity

By cleaving crystals of YBa2Cu3O7 in high vacuum and evaporating Au in situ, we have fabricated Au-YBa2Cu3O7 junctions with very low contact resistance. Below Tc, the specified contact resistivity drops by three decades to an estimated value 2×10−9 Ω cm2 at 87.3 K. We emphasize the importance of correcting for spreading resistance in such studies. We also discuss the ideal contact resistivity, and possible contributions to the measured resistance very near Tc.