Anomalous Order in $R_3{\text{Ni}}_{30}{\text{B}}_{10}$ $(R=\text{La},\text{Ce})$

We report the synthesis of single crystals of the $R_3{\text{Ni}}_{30}{\text{B}}_{10}$ $(R=\text{La},\text{Ce})$ system which realizes the tetragonal $P4\mathrm{/}nmm$ (No. 129) space group. We performed single crystal, transmission X-ray diffraction measurements to determine the crystal structure. Additionally, we characterized the samples through magnetization, resistivity, and heat capacity measurements. The $R=\text{Ce}$ system exhibits mixed-valence states and we observe maxima in the heat capacity at $T_1^{\ast }=6\text{K}$ and $T_2^{\ast }=2\text{K}$ (both absent for $R=\text{La}$) with no corresponding features in the resistivity or magnetization. We discuss the potential roles of multipolar and short-ranged/partial order in connection to the $T_1^{\ast }$ anomalous order.