Fig. 1: Emergence of an intermediate phase between T^* and T_CDW inside the CDW state of ScV₆Sn₆.

a ScV₆Sn₆ structure generated using VESTA (left), with the Kagome lattice in the ab-plane (right). b ab-plane resistivity \({{\rm{\rho }}}\) showing sharp drops when the sample is cooled through \({{{\rm{T}}}}_{{{\rm{CDW}}}}\) and \({{{\rm{T}}}}^{*}\). Left inset: resistivity near transition temperatures. Right inset: image of the measured ScV₆Sn₆ single crystal sample. c Specific heat capacity \({C}_{p}\) exhibits a major peak at \({{{\rm{T}}}}_{{{\rm{CDW}}}}\) and a minor peak at \({T}^{*}\), serving as direct evidence for double phase transitions. Inset: \({C}_{p}\) near transition temperatures. Dots are individual data points. d Optical reflectivity measured with the 1.55 \({{\rm{\mu }}}{{\rm{m}}}\) optical beam focused onto a single spot on the ab-plane surface. The sharp changes at both \({T}_{{CDW}}\) and \({T}^{*}\) demonstrate the intrinsic nature of the “double transition”. Reflectivity measurements at various spots are presented in Supplementary Fig. 1. Inset: reflectivity near transition temperatures.