We have applied pressure (i.e., stress) to single-crystal ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ along the c axis to reduce the separation between the copper-oxygen planes. For the normal state, increasing pressures up to ∼1 kbar causes the c-axis resistivity to decrease dramatically and tend toward a metalliclike temperature dependence. No change is observed in the ab-plane resistivity. The superconducting $T_c$ increases with decreasing interplane separation with ${\mathrm{dT}}_c$/dP≊0.1 K/kbar. Some implications of these findings for normal-state conduction mechanisms and models of high-$T_c$ superconductivity for ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ are discussed.

• Received 5 August 1988

DOI:https://doi.org/10.1103/PhysRevB.39.4231