High-pressure investigation of the heavy-fermion antiferromagnet U3Ni5Al19

Measurements of magnetic susceptibility, specific heat, and electrical resistivity at applied pressures up to 55 kbar have been carried out on single crystals of the heavy-fermion antiferromagnet U3Ni5Al19, which crystallizes in the Gd3Ni5Al19 orthorhombic structure with two inequivalent U sites. At ambient pressure, an upturn of the specific heat and T-linear electrical resistivity below 5 K indicate non-Fermi liquid (NFL) behavior in the presence of bulk antiferromagnetic order at T-N=23 K. Electrical resistivity measurements reveal a crossover from non-Fermi liquid to Fermi liquid behavior at intermediate pressures between 46 and 51 kbar, followed by a return to NFL T-3/2 behavior at higher pressures. These results provide evidence for an ambient pressure quantum critical point and an additional antiferromagnetic instability at P(c)approximate to60 kbar.