ZERO RESISTANCE ABOVE 90K IN SUPERCONDUCTING OXIDE Tm-Ba-Cu-O

Superconducting transition has been observed by electrical resistance and a.c. magnetic susceptibility measurements in Tm_xBa_1-xCuO_3-y with x=0.6 and 0.7 and y>0. The highest T_c of the samples measured is observed in Tm_0.6- Ba_0.4CuO_3-y which has the T_c(mid)=91K with ΔT_c=0.5K, and T_c(ρ=0)=90.1K. The a. c . magnetic susceptibility measurements show a very strong diamagnetism at the temperature of resistive midpoint.