High-pressure investigation of the heavy-fermion antiferromagnet U 3 Ni 5 Al 19

Measurements of magnetic susceptibility, specific heat, and electrical resistivity at applied pressures up to $55\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$ have been carried out on single crystals of the heavy-fermion antiferromagnet ${\mathrm{U}}_{3}{\mathrm{Ni}}_{5}{\mathrm{Al}}_{19}$, which crystallizes in the ${\mathrm{Gd}}_{3}{\mathrm{Ni}}_{5}{\mathrm{Al}}_{19}$ orthorhombic structure with two inequivalent U sites. At ambient pressure, an upturn of the specific heat and $T$-linear electrical resistivity below $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ indicate non-Fermi liquid (NFL) behavior in the presence of bulk antiferromagnetic order at ${T}_{N}=23\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Electrical resistivity measurements reveal a crossover from non-Fermi liquid to Fermi liquid behavior at intermediate pressures between 46 and $51\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$, 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 ${P}_{c}\ensuremath{\approx}60\phantom{\rule{0.3em}{0ex}}\mathrm{kbar}$.