Paramagnetic resonance of ${\mathrm{Cu}}^{2+}$ ions in the superconductor ${\mathrm{Y}}_{0.2}$${\mathrm{Ba}}_{0.8}$${\mathrm{CuO}}_{\mathrm{x}}$

A strong paramagnetic resonance signal characteristic of ${\mathrm{Cu}}^{2+}$ ions in ‖$x^2$-$y^2$〉 states is observed in the high-$T_c$≊90 K superconductor ${\mathrm{Y}}_{0.2}$${\mathrm{Ba}}_{0.8}$${\mathrm{CuO}}_{\mathrm{x}}$. The line intensity of the ioniclike signal shows a deviation from Curie behavior at T≳$T_c$. It is speculated that the phase that is responsible for the signal is an example of an Anderson lattice with an unusually high Kondo temperature.