Normal-state properties of $A{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-y}$ compounds ($A=\mathrm{Y}\mathrm{and}\mathrm{Gd}$): Electron-electron correlations

Resistivity, thermoelectric power, Hall effect, and magnetic susceptibility measurements are reported in the normal state of the high-$T_c$ compounds $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-y}$ and $\mathrm{Gd}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-y}$. The results are different from those expected for an uncorrelated metallic band. We suggest that Coulomb interactions are important and that the interaction energy is comparable to or larger than the uncorrelated bandwidth, leading to moderately heavy-fermion-like behavior in the normal state. The Sommerfeld coefficient $\gamma$ calculated from the susceptibility indicates that the electron-phonon coupling constant at $T_c$ is not unusually large.