Multiple and weak-coupling charge-density-wave transitions inY5Ir4Si10

Physical characterizations on the ternary compound ${\mathrm{Y}}_5{\mathrm{Ir}}_4{\mathrm{Si}}_{10}$ by using electrical resistivity $\left(\rho \right)$, Hall coefficient $\left(R_H\right)$, magnetic susceptibility $\left(\chi \right)$, specific heat $\left(C_P\right)$, thermal conductivity $\left(\kappa \right)$, and thermoelectric power are reported. For all measured transport and thermodynamic properties, successive anomalies due to charge-density-wave (CDW) formation were observed. In contrast to the strong-coupled nature of the phase transitions found in the isostructural compounds $R_5{\mathrm{Ir}}_4{\mathrm{Si}}_{10}$ $\left(R=\mathrm{Dy}\text{−}\mathrm{Lu}\right)$, ${\mathrm{Y}}_5{\mathrm{Ir}}_4{\mathrm{Si}}_{10}$ 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.