Semiconducting behaviour in the Remeika phase: Pr₃Ir₄Ge₁₃

We report the magnetic, electronic and transport properties of the quasi-skutterudite compound Pr₃Ir₄Ge₁₃ by means of magnetic susceptibility χ(T), electrical resistivity ρ(T), specific heat C_p(T), thermal conductivity κ(T), thermoelectric power S(T) and Hall coefficient R_H(T) measurements. Pr₃Ir₄Ge₁₃ does not show any phase transition down to 1.9 K. Magnetic, and specific measurements show that the system possesses a crystal electric field singlet ground state that is separated from the first excited state by about 37 K. ρ(T) shows a negative temperature coefficient of resistance for the whole temperature range studied and which can be explained in terms of Mott's impurity band conduction mechanism. R_H(T) measurements show that Pr₃Ir₄Ge₁₃ is a low-carrier density semiconductor and its transport properties indicate a metallic-non metallic cross over behaviour. Large Seebeck coefficient was observed for the entire temperature range of investigation, and the analysis of temperature variation of S and S∕T showed no sign of strong correlation between the Pr 4f² and conduction electron states near Fermi level.