The $\mathrm{Ce}{\mathrm{Ni}}_4\mathrm{Al}$ compounds have been studied using the magnetic susceptibility, specific heat, electrical resistivity and x-ray photoemission spectroscopy (XPS) measurements. The XPS experiments were supported by the theoretical calculations employing the TB LMTO method. The estimation of the hybridization, $\Delta$, between the $f$-level and the conduction states was based on the XPS measurements of the $\mathrm{Ce}\left(3d\right)$ states and revealed a small value of $\Delta \approx 37\mathrm{meV}$ accompanied by a nearly full $f$-occupancy $(n_f\approx 0.88)$. The temperature measurements of the dc susceptibility have shown paramagnetic behavior fulfilling the Curie-Weiss law with ${\mu }_{\mathrm{eff}}=0.6{\mu }_{\mathrm{B}}∕\mathrm{f.u}$. Experimental values of the specific heat coefficient $\gamma =29{\mathrm{mJK}}^{-2}{\mathrm{mol}}^{-1}$ and the Debye temperature ${\theta }_D=315\mathrm{K}$ have been obtained. The electrical resistivity measurements revealed a presence of a minimum at about $16\mathrm{K}$.

Dicarboxylic acids are interesting for crystal engineering due to their ability of hydrogen bond formation. To find a relationship between the molecular structure and the properties of proton conducting materials, we synthesized two compounds of benzimidazole with dicarboxylic acids of different chain length: glutaric and pimelic acids. The structure of the compounds was determined by X-ray diffraction and compared with molecular arrangement studied by ¹³C CP/MAS NMR spectroscopy supported by Density Functional Theory computations for benzimidazole. Benzimidazole was found to form salt with glutaric acid in a 1 : 1 ratio and monoclinic layer-type structure with P2₁/n space group. Flat layers, parallel to (−102) plane, are built of glutaric acid molecules linked into rectangular-type chains by O–H⋯O bonds and benzimidazole molecules attached to the chains by N–H⋯O bonds. The molecule of the benzimidazole compound with pimelic acid contains two benzimidazole rings and one pimelic acid chain. The structure with alternating layers, built of two groups of benzimidazole dimers and layers of pimelic acid chains, belongs to P2₁/n space group. The acid layers are built of pimelic acid molecules linked by O–H⋯O hydrogen bonds into chains parallel to [30−1] direction and the benzimidazole dimers are linked to the acid layers by N–H⋯O bonds. Impedance spectroscopy studies in wide frequency and temperature range of pellets made of powdered compounds enabled to separate the contributions of crystalline and grain boundary parts to the electric conductivity. The conductivity (averaged over all directions) of the crystalline compounds of benzimidazole with glutaric and pimelic acid is characterized by activation energy of 2.5 eV and 1.6 eV, respectively, which is in an agreement with the hydrogen bond network in the materials.