Low-temperature transport and thermodynamic properties of dense Kondo alloys Ce₈Pd₂₄(Al_1−xSn_x)

The alloys Ce₈Pd₂₄(Al_1−xSn_x) with 0≤x≤1 were studied by means of electrical resistivity, thermal conductivity, thermoelectric power, magnetic susceptibility and magnetization measurements. In the entire composition range, an antiferromagnetic (AFM) long-range ordering has been established at low temperatures, with the Néel temperature increasing linearly from T_N = 4.3 K for Ce₈Pd₂₄Al to T_N = 7 K for Ce₈Pd₂₄Sn. Below T_N, the electrical resistivity is dominated by scattering conduction electrons on spin-wave excitations. In the paramagnetic state, the electrical transport in the alloys with 0≤x≤0.7 reveals both coherent Kondo lattice scattering and crystal-electric field (CEF) effect, while that in the alloys with x≥0.8 appears governed by CEF only. Above T_N, all the alloys exhibit well localized magnetic behavior due to trivalent Ce ions. At high temperatures, the thermoelectric power can be interpreted in terms of a phenomenological resonance model giving an estimate of the CEF effect. The thermoelectric figure of merit of Al-rich alloys is small compared to those of commercial thermoelectric materials.