Resistivity measurements were performed for the itinerant Ising-type ferromagnet URhAl at temperatures down to 40 mK under high pressure up to 7.5 GPa, using single crystals. We found that the critical pressure of the Curie temperature exists at arou
nd $P_c$ ~ 5.2 GPa. Near $P_c$, the $A$-coefficient of the $AT^{2}$ Fermi-liquid resistivity term below $T^*$ is largely enhanced with a maximum around 5.2-5.5 GPa. Above $P_c$, the exponent of the resistivity $rho(T)$ deviates from 2. At $P_c$, it is close to $n = 5/3$, which is expected by the theory of three-dimensional ferromagnetic spin fluctuations for a 2nd-order quantum-critical point (QCP). However, $T_C(P)$ disappears as a 1st-order phase transition, and the critical behavior of resistivity in URhAl cannot be explained by the theory of a 2nd-order QCP. The 1st-order nature of the phase transition is weak, and the critical behavior is still dominated by the spin fluctuation at low temperature. With increasing pressure, the non-Fermi-liquid behavior is observed in higher fields. Magnetic field studies point out a ferromagnetic wing structure with a tri-critical point (TCP) at ~ 4.8-4.9 GPa in URhAl. One open possibility is that the switch from the ferromagnetic to the paramagnetic states does not occur simply but an intermediate state arises below the TCP as suggested theoretically recently. Quite generally, if a drastic Fermi-surface change occurs through $P_c$, the nature of the interaction itself may change and lead to the observed unconventional behavior.
We have performed low-temperature specific-heat measurements in magnetic fields for a single crystal UBe13. It has been observed that our sample exhibits a superconducting transition at an intermediate temperature between previously reported values f
or two variant samples called H type and L type. The specific heat C(T) of our sample shows a T^3 behavior in the temperature range below 0.7 Tc, which is similar to the behavior of the H-type sample, suggesting the existence of point nodes in the superconducting gap function. We have obtained the upper-critical-field curves Hc2 for the [001], [110], and [111] crystal axes, which show no anisotropy at least down to the lowest measured temperature of 0.5 K. We have also derived the Maki parameter kappa2, and it has been revealed that the kappa2 steeply decreases isotropically upon cooling just below Tc. Paramagnetic effects and the symmetry of Cooper pairing of UBe13 are discussed.
