Anisotropic thermoelectric power in single crystalline Mg1-xAlxB2 compounds

The thermoelectric power of single crystalline Mg 1−x Al x B 2 compounds is measured and analyzed along the main crystallographic directions ( ab -plane and c -axis direction). It is shown that the classical model of thermoelectric power with phonon drag and diffusion terms provides satisfactory explanation of the temperature dependence of the Seebeck parameter S ( T ). Agreement of S ( T ) with the study of resistivity is achieved with some variation of the Debye temperature being a model-sensitive parameter. Presence of positive and negative charge carriers is observed and competing contributions of the π and σ bands are discussed.