Promising thermoelectric properties of heavy-fermion semimetal Pr3Os4Ge13

Abstract

Here we report the magnetic, electronic and thermal transport properties of the heavy-fermion semimetal Pr3Os4Ge13 with a cage-like structure by means of magnetic susceptibility, χ(T), isothermal magnetization, M(B, T), electrical resistivity, ρ(B, T), Hall coefficient, RH(T), specific heat, Cp(T), thermal conductivity, κ(T) and thermoelectric power, S(T). ρ(T) and RH(T) show semimetallic features in a manner that mimics a thermal activated behaviour with an activation energy, Δ/kB = 6.5 K indicating the opening of a small energy gap in the material. At low temperatures, a Sommerfeld coefficient, γ = 128 mJ (mol−1 K−2) observed indicates a mass enhancement of the quasiparticles at low temperatures which bears witness to a heavy fermion state in Pr3Os4Ge13. A Wilson–Sommerfeld ratio, WR and the dimensionless ratio, S/γT of 1.01 and 0.62 ± 0.018 observed, respectively, are in good agreement with the Fermi liquid scenario. S(T) and RH(T) reveal hole dominated transport (p-type material) with a relatively large room temperature value of S(T) = 32.85 ± 0.98 μV K−1. A room temperature low value of κ(T) = 1.61 W K−1 m−1 leads to a thermoelectric figure of merit, ZT = 0.03 ± 0.001 which is comparable to values achieved in several clathrates around the same temperature. Features from S(T) and ρ(T) favour the realization of a higher ZT value at elevated temperatures.