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An electronic solid with itinerant carriers and localized magnetic moments represents a paradigmatic strongly correlated system. The electrical transport properties associated with the itinerant carriers, as they scatter off these local moments, have been scrutinized across a number of materials. Here, we analyze the transport characteristics associated with ultraclean PdCrO ${}_2$ —a quasi-two-dimensional material consisting of alternating layers of itinerant Pd-electrons and Mott-insulating CrO ${}_2$ layers—which shows a pronounced regime ofT-linear resistivity over a wide range of intermediate temperatures. By contrasting these observations to the transport properties in a closely related material PdCoO ${}_2$ , where the CoO ${}_2$ layers are band-insulators, we can rule out the traditional electron–phonon interactions as being responsible for this interesting regime. We propose a previously ignored electron-magneto-elastic interaction between the Pd-electrons, the Cr local moments and an out-of-plane phonon as the main scattering mechanism that leads to the significant enhancement of resistivity and aT-linear regime in PdCrO ${}_2$ at temperatures far in excess of the magnetic ordering temperature. We suggest a number of future experiments to confirm this picture in PdCrO ${}_2$ as well as other layered metallic/Mott-insulating materials. 

In bulk ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ , the strong sensitivity of the superconducting transition temperature $T_{\text{c}}$ to nonmagnetic impurities provides robust evidence for a superconducting order parameter that changes sign around the Fermi surface. In superconducting epitaxial thin-film ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ , the relationship between $T_{\text{c}}$ and the residual resistivity ${\rho }_0$ , which in bulk samples is taken to be a proxy for the low-temperature elastic scattering rate, is far less clear. Using high-energy electron irradiation to controllably introduce point disorder into bulk single-crystal and thin-film ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$ , we show that $T_{\text{c}}$ is suppressed in both systems at nearly identical rates. This suggests that part of ${\rho }_0$ in films comes from defects that do not contribute to superconducting pairbreaking and establishes a quantitative link between the superconductivity of bulk and thin-film samples. Published by the American Physical Society2024