High field magnetotransport and specific heat in YbAgCu4

Abstract

The electrical resistivity (rho) and magnetoresistance of polycrystalline YbAgCu4 have been measured at temperatures between 25 mK and 300 K, and at magnetic fields (B) up to 18 T. The magnetoresistance (rho(B) - rho(0))/rho(0)) is positive at all temperatures below 200 K and reaches its maximum of 60% at 18 T and 25 mK. The field-and temperature-dependent resistivity does not scale in a simple way. The opposite sign of the magnetoresistance at ambient and high pressure can be explained qualitatively by crystal-field effects lifting the degeneracy of the J = 7/2 groundstate. The linear coefficient of the specific heat (gamma) measured at fields up to 10 T shows a quadratic field dependence. We did not find a linear relation between gamma(2) and A, the T-2-coefficient of the temperature-dependent resistivity, with the applied magnetic field as the implicit parameter.