Ionic size and atomic disorder effects on the charge-density-wave transitions inR5Ir4Si10(R=Dy−Lu)

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We report the systematic investigations of specific heat $C,$ thermal conductivity $\ensuremath{\kappa},$ and thermoelectric power on the rare-earth--transition-metal ternary compounds ${R}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10}(R$ = Dy, Ho, Er, Tm, Yb, and Lu) as a function of temperature. For all measured thermal properties, pronounced anomalous responses were observed near the charge-density-wave (CDW) transition temperature ${T}_{P}$ in these compounds (except $R=\mathrm{Yb}).$ Particularly, the complex temperature-dependent thermal transport properties observed in these materials indicate very complicated heat transport processes during the phase transitions. Although these phase transitions can be associated with the CDW formation, the measured anomalies are considerably large, in contrast to those found in other weak-coupled CDW materials. In addition, it is found that ${T}_{P}$ decreases linearly with the decreasing ionic radius of rare-earth elements from ${\mathrm{Dy}}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10}$ to ${\mathrm{Lu}}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10},$ but it increases nonlinearly with x in $({\mathrm{Lu}}_{1\ensuremath{-}x}{\mathrm{Er}}_{x}{)}_{5}{\mathrm{Ir}}_{4}{\mathrm{Si}}_{10}.$ These observations indicate that both ionic-size and atomic-disorder effects play important roles for the CDW transitions in this class of materials.