Transport properties of the anisotropic itinerant-electron metamagnet UCoAl

Magnetoresistance (MR), Hall resistivity, and thermoelectric power in UCoAl, which exhibits a metamagnetic transition (MT) at low temperatures, have been investigated. Across MT, the MR shows a steplike decrease and increase for the transverse and longitudinal geometries, respectively. The temperature dependence of MR indicates that the magnetic scattering due to the spin fluctuations largely contributes to the electrical resistivity around 17 K. The Hall coefficient and the thermoelectric power show drastic changes associated with MT. Both in the low- and high-field states, the extraordinary Hall effect dominates in the temperature dependence of Hall coefficient. The temperature dependence of thermoelectric power can be qualitatively explained by an extended s-d model considering the $5f$ band structure.