Electron-electron and electron-phonon collision cross sections in CsV3Sb5
AV3Sb5 (A=K, Rb, Cs) are kagome metals and superconductors, attracting much recent attention as nexus of multiple quantum states. Here, through a systematic study of electric and thermal transport of CsV3Sb5, we identify it as a metallic Fermi liquid with moderate electronic correlations ans strong electron-phonon (e-ph) collision cross section. We observe contributions to the inelastic electrical resistivity, each dominating within a distinct temperature window. The prefactor of the T2 is consistent with the Kadowaki-Woods scaling for a Fermi liquid with moderate correlation. By performing thermal conductivity measurements at zero and finite magnetic field, we separate the electronic and the lattice contributions to the thermal conductivity. The Wiedemann-Franz law is satisfied in the zero-temperature limit, while a downward deviation emerges at finite temperature due to the mismatch between the prefactors of the electrical and thermal quadratic resistivities, as reported in other metals. The Bloch-Gr\"uneisen description of electron-phonon scattering successfully accounts for both electronic thermal and electrical transport, indicating a remarkably large e-ph collision cross section in CsV3Sb5.