Resonant x-ray diffraction measurements in charge ordered kagome superconductors KV3Sb5 and RbV3Sb5.

We report on (resonant) x-ray diffraction experiments on the normal state properties of kagome- lattice superconductors KV3Sb5 and RbV3Sb5. We have confirmed previous reports indicating that the charge density wave phase is characterized by a doubling of the unit cell in all three crystallographic directions. By monitoring the temperature dependence of Bragg peaks associated with the charge density wave phase, we ascertained that it develops gradually over several degrees, as opposed to CsV3Sb5, where the charge density wave peak intensity saturates promptly just below the charge density wave transition temperature. Diffraction measurements close to the V K edge and the Sb L1 edge show no sensitivity to inversion- or time-symmetry breaking, which are claimed to be associated with the onset of the charge density wave phase. Resonant diffraction intensity observed at the Sb L1 edge is associated with the anisotropy of the electron density of some of the Sb ions.