Effect of La substitution on thermopower in Kondo lattice CeNiAl4

• Negative thermopower for CeNiAl4 after substituting Ce with La.
• Heavy fermion behaviour at low temperatures.
• Magnetic field reduces the thermopower values.
• Predomination of the energy scale determined by the Kondo temperature.

The temperature dependence of the thermopower S(T) for Ce1−xLaxNiAl4 alloys have been studied. Thermopower of CeNiAl4 Kondo lattice system has larger value than for usual metals, reflecting enhanced electronic density of states near the Fermi level. In comparison to CeNiAl4, the substitution of Ce by La drastically reduces the S(T) values. The S(T) dependence of Ce1−xLaxNiAl4 exhibits positive or negative peaks around 30–40 K. The peak position and its absolute value depend on the La content. The S(T) shows a strong temperature dependence at low temperatures, which is consistent with the temperature dependence of the electrical resistivity. Additionally, it is observed that the applied magnetic field slightly reduces the S(T) values.