Superconductivity near 90 K in the Lu-Ba-Cu-O system

Superconducting onsets near 90 K are observed in multiphase samples with nominal composition ${\mathrm{Lu}}_{1.8}$ ${\mathrm{Ba}}_{0.2}$ ${\mathrm{CuO}}_4$. Results of electrical resistance, mutual inductance, and dc magnetization measurements are reported. Magnitude of superconducting transitions indicates that about 2% of the best sample is superconducting.