Thermoelectric power study of Eu_{1 - x} La_x B₆ ( x = 0.0, 0.1, 0.2 )

Temperature-dependent thermoelectric power (TEP) was measured in the range of 2 K < T < 300 K for single crystals of Eu_{1 - x} La_x B₆ ( x = 0.0, 0.1, and 0.2). For Eu_{1 - x} La_x B₆ ( x = 0.0 and 0.1), the TEP shows negative values in the whole temperature range, consistent with the fact that dominant charge carriers in Fermi surface are electrons. However, for Eu_{1 - x} La_x B₆ ( x = 0.2 ), a sign change of the TEP from negative to positive value is observed at about 28 K, which is consistent with the sign reversal of Hall resistivity of the same compound. We surmise that the anomalous sign reversal seems to be accompanied by a magnetic transition from ferromagnetic to antiferromagnetic with La doping in Eu_{1 - x} La_x B₆.