All high T_c edge junctions and SQUIDs

We present the first observations of superconducting quantum interference in multilevel, all high Tc, lithographically patterned edge junction structures. The current-voltage characteristics are nonhysteretic and have well-defined critical currents. The dynamic resistance is independent of current above the critical current. These devices show periodic sensitivity to magnetic fields and low levels of magnetic hysteresis up to temperatures around 60 K.