Thermal and electrical transport properties of UCu$_{4+x}$Al$_{8-x}$

The UCu$_{4+x}$Al$_{8-x}$ family crystallizes in the tetragonal ThMn$_{12 }$- type structure in the range from 0.1$\le $ x$\le $ 1.95. It has been reported that the Cu-poor compounds show antiferromagnetic long-range order, followed by a transition at x=1.15 to a heavy fermion behavior. We report on the results of thermal conductivity and the Seebeck coefficient as a function of temperature (1.8-300K). Thermal conductivity data are consistent with previously published electrical resistivity data. The Seebeck coefficient measurements, S, confirm the peaks at T$_{N}$ for the antiferromagnetic compounds. We also measured electrical resistivity as function of very low temperature from 75mK to 4K and in magnetic field up to 6Tesla for UCu$_{6}$Al$_{2}$, UCu$_{5.75}$Al$_{6.25}$, UCu$_{5.5}$Al$_{6.5}$ and UCu$_{5.25}$Al$_{6.75}$. UCu$_{5.75}$Al$_{6.25 }$which was reported as non-Fermi liquid (NFL) compound shows quantum critical point induced by magnetic field. These results provide some insight about the underlying mechanisms to the apparent NFL behavior in UCu$_{5.75}$Al$_{6.25}$ compound.