Nontrivial physics in the twisted kagome antiferromagnet ErPdPb

Twisted kagome systems (ZrNiAl structure prototype) type structure involving rare earth elements have recently attracted attention due to the fact that lower local symmetry and strong anisotropy  enable intriguing properties such as 2D Ising and Potts spin-ice, large magnetocaloric effect, complex magnetic ordering, and multiple magnetization steps. Here, we report the synthesis of single crystals of ErPdPb, whith a twisted Er kagome lattice, and we investigate its magnetic, electronic, and thermal properties. It orders antiferromagnetically below 2.2 K, as observed across magnetic, transport, and heat capacity measurements. Magnetization measurements reveal 1/3 metamagnetic steps along the c-axis below the Néel temperature, consistent with the three Ising spins along c in the unit cell. A pronounced anisotropy between in-plane and out-of-plane resistivity is observed throughout the temperature range of 1.8–300 K. High-temperature susceptibility shows Curie-Weiss (CW) behavior with large CW temperatures of ~30 K, and of the opposite sign for the in- or out-of-plane fields, indicating a strong frustration and a dominant role of anisotropic diagonal exchange. Heat capacity measurements show a broad hump at 2.2 K, with an additional increase below 0.5 K.  Density functional theory (DFT) calculations show three strongly 1D bands corresponding to three PdPb₃ chains per unit cell, running along c (the calculated transport anisotropy is consistent with the experiment), as well as an unusual saddle point at Г right at the Fermi level, strongly spin-split (~20 meV) in the forced ferromagnetic state. DFT also predicts a strong easy-axis anisotropy, consistent with the experiment. These are all Hallmarks of interesting and unusual physical properties deserving further investigation.