Multiple and weak-coupling charge-density-wave transitions in Y5Ir4Si10

Physical characterizations on the ternary compound Y5Ir4Si10 by using electrical resistivity srd, Hall coefficient sRHd, magnetic susceptibility sxd, specific heat sCPd, thermal conductivity skd, and thermoelectric power are reported. For all measured transport and thermodynamic properties, successive anomalies due to chargedensity-wave (CDW) formation were observed. In contrast to the strong-coupled nature of the phase transitions found in the isostructural compounds R5Ir4Si10 sR=Dy-Lud, Y5Ir4Si10 could be described as a weak-coupled CDW system. Most interestingly, the complex temperature-dependent thermoelectric power and sign reversal of Hall coefficient in this material indicate a drastic modification of Fermi surface and a sudden change of the band structure, associated with the electron-hole asymmetry at the transitions.