We report the synthesis, crystal structure, and characterization by means of single-crystal x-ray diffraction, neutron powder diffraction, and magnetic, thermal, and transport measurements of the new heavy-fermion compounds ${\mathrm{Ce}}_2{M\mathrm{Al}}_7{\mathrm{Ge}}_4$ $(M=\text{Co},\text{Ir},\text{Ni},\text{Pd})$. These compounds crystallize in a noncentrosymmetric tetragonal space group $\mathit{P}\overline{4}{2}_{1}m$, consisting of layers of square nets of Ce atoms separated by Ge-Al and M-Al-Ge blocks. ${\mathrm{Ce}}_2{\mathrm{CoAl}}_7{\mathrm{Ge}}_4,{\mathrm{Ce}}_2{\mathrm{IrAl}}_7{\mathrm{Ge}}_4$, and ${\mathrm{Ce}}_2{\mathrm{NiAl}}_7{\mathrm{Ge}}_4$ order magnetically below $T_M=1.8$, 1.6, and 0.8 K, respectively. There is no evidence of magnetic ordering in ${\mathrm{Ce}}_2{\mathrm{PdAl}}_7{\mathrm{Ge}}_4$ down to 0.4 K. The small amount of entropy released in the magnetic state of ${\mathrm{Ce}}_{2}M{\mathrm{Al}}_7{\mathrm{Ge}}_4$ $(M$ = Co, Ir, Ni) and the reduced specific heat jump at $T_M$ suggest a strong Kondo interaction in these materials. ${\mathrm{Ce}}_2{\mathrm{PdAl}}_7{\mathrm{Ge}}_4$ shows non-Fermi liquid behavior, possibly due to the presence of a nearby quantum critical point.

• Received 1 October 2015
• Revised 4 April 2016

DOI:https://doi.org/10.1103/PhysRevB.93.205141