Metallic super-heavy fermion compounds can be used for adiabatic demagnetization cooling to temperatures well below 0.1 K.

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We show that the cubic compound PbBi2 is a topological semimetal hosting a sixfold band touching point in close proximity to the Fermi level. Using angle-resolved photoemission spectroscopy, we map the band structure of the system, which is in good agreement with results from density functional theory. Further, by employing a low energy effective Hamiltonian valid close to the crossing point, we study the effect of a magnetic field on the sixfold fermion. The latter splits into a total of twenty Weyl cones for a Zeeman field oriented in the diagonal, (111) direction. Our results mark cubic PbBi2 as an ideal candidate to study the transport properties of gapless topological systems beyond Dirac and Weyl semimetals.

Layered van der Waals materials of the family TaTMTe4 (TM = Ir, Rh, Ru) are showing interesting electronic properties. We report the growth and characterization of TaIrTe4, TaRhTe4, TaIr1–x Rh x Te4 (x = 0.06, 0.14, 0.78, 0.92), Ta1+x Ru1–x Te4 single crystals. X-ray powder diffraction confirms that TaRhTe4 is isostructural to TaIrTe4. All these compounds are metallic with diamagnetic behavior. Below T ≈ 4 K we observed signatures of the superconductivity in the TaIr1–x Rh x Te4 compounds for x = 0.92. All samples show weak quadratic-in-field magnetoresistance (MR). However, for TaIr1–x Rh x Te4 with x ≈ 0.78, the MR has a linear term dominating in low fields that indicates the presence of Dirac cones in the vicinity of the Fermi energy. For TaRhTe4 series the MR is almost isotropic. Electronic structure calculations for TaIrTe4 and TaRhTe4 reveal appearance of the Rh band close to the Fermi level.

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