Effect of Si/Ge ratio on resistivity and thermopower in Gd5SixGe4−x magnetocaloric compounds

► Effect of Si/Ge ratio on microstructure, magneto-structural transitions, resistivity (ρ) and thermopower S(T) behaviour has been investigated in Gd5SixGe4-x compounds with x=1.7, 2.0, 2.2 and 2.3. ► Microstructural studies reveal the presence of a Gd5(Si,Ge)4 -matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). ► The resistivity behaviour has shown good correlation with the microstructural studies. A large change in thermopower of -8μV/K was obtained at the magneto-structural transition for the x=2 compound. ► The resistivity and change in thermopower values were high for the alloys with Si/Ge ratio ≤1 compared to that of the alloys with Si/Ge ratio >1.