Unusual antiferromagnetism and field-induced transitions in tetragonal CeLiBi2

We report the discovery and systematic study of single crystals of CeLiBi$_2$ using magnetization, specific heat, and resistivity measurements. CeLiBi2 resides in a large family of CeTX$_2$ (T = transition metal or alkali; X = pnictogen) $P4/nmm$ materials showing quantum criticality [1-2], successive metamagnetic transitions [3], and nematic order [4]. In this family, the magnetic ground state is closely linked to the crystalline electric field ground state derived from splitting the $J = 5/2$ Ce$^{3+}$ spin orbit coupled manifold into a series of three Kramers doublets. When the ground state is comprised of a $\Gamma_7$ doublet, the materials exhibit antiferromagnetism, and if the ground state is a $\Gamma_6$ doublet, ferromagnetism arises [5]. Surprisingly, the asymmetric magnetic susceptibility response of CeLiBi$_2$ indicates the ground state Kramers doublet is $\Gamma_6$, yet a sharp decrease in susceptibility at $T_N = 3.4$ K suggests the ordered state is antiferromagnetic. Specific heat and resistivity measurements further indicate antiferromagnetism in CeLiBi$_2$. The sharp specific heat anomaly and cusp in resistivity near $3.4$ K shift to lower temperatures with increasing external ab-plane magnetic field up to $\mu_0H = 3$ T, above which the features broaden. Resistivity versus field along the $c$-axis indicates two additional field induced transitions at $\mu_0H = 2$ T and $6$ T with successively increasing magnetoresistance. The phase boundaries between these field induced states are tracked via thermal expansion measurements.