Superconducting and antiferroquadrupolar (AFQ) transitions in a Pr-based compoundPrRh 2 Zn 20 have been found to occur simultaneously at T c =T Q =0.06 K. The superconducting transition manifests itself by zero resistance and large diamagnetic susceptibility. The specific heat exhibits a Schottky anomaly peaking at 14 K and magnetization curves measured at 2 K show anisotropic behaviors. The analysis of these data indicates that the crystalline electric field (CEF) ground state of the trivalent Pr ion is the non-Kramers Γ 3 doublet with the quadrupolar degrees of freedom. A sharp peak in the specific heat at 0.06 K has been attributed not to the superconducting transition but to the AFQ transition because the ordering temperature T Q decreases in B || [100] but increases in B|| [110] and B || [111] with increasing B up to 6 T. This anisotropic behavior of T Q (B) can be well explained by a two-sublattice mean-field calculation, which corroborates the AFQ ordered state below T Q . The entropy release at T Q is only 10% of Rln2 expected for the Γ 3 doublet, suggesting possible interplay between the quadrupolar degrees of freedom and the superconductivity.

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We have investigated the low temperature quadrupolar phenomena of the non-Kramers system PrRh 2 Zn 20 under magnetic fields in the [100] and [110] directions. Our experiments reveal the B-T phase diagram of PrRh 2 Zn 20 involving four electronic states regardless of the field direction, namely, a non-Fermi liquid (NFL) state, an antiferro-quadrupolar (AFQ) ordered state, a novel heavy-fermion (HF) state, and a field-induced singlet (FIS) state. In the wide range of the NFL state, the resistivity can be well scaled by a characteristic temperature, suggesting the realization of the quadrupole Kondo effect. The HF state exhibits a Fermi liquid behavior with a large A coefficient of the T 2 term in the resistivity, suggesting the formation of nontrivial heavy quasi-particles. The FIS state results from the considerable splitting of a non-Kramers doublet by a magnetic field. The phase diagram shows a large anisotropy with respect to the field direction. It is found that the anisotropy of the phase diagram can be explained in terms of that of the energy splitting of the non-Kramers doublet by a magnetic field. This indicates that the low temperature properties of PrRh 2 Zn 20 are governed by the non-Kramers doublet, namely, quadrupole degrees of freedom. Since a similar phase diagram has been obtained for the related compound PrIr 2 Zn 20 , it is expected that the B-T phase diagram constructed in this work is universal throughout non-Kramers systems.arXiv:1702.07686v1 [cond-mat.str-el]

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The caged compound LaRu 2 Zn 20 exhibits a structural transition at T S =150 K, whose driving mechanism remains elusive. We have investigated atomic dynamics by the measurements of specific heat C and inelastic X-ray scattering (IXS). The lattice part of the specific heat C lat divided by