Antiferromagnetic Kondo lattice in the layered compounds Re$_{2}$NiGa$_{9}$Ge$_{2}$ (Re$=$Ce, Pr, Sm)

Intermetallic compounds containing rare-earth/actinide elements with 4f/5f electrons have formed a special family of strongly correlated materials, i.e. heavy fermion systems. We have recently found a new layered rare earth intermetallic system showing moderate heavy fermion behavior: Re$_{2}$NiGa$_{9}$Ge$_{2}$ (Re$=$Ce, Sm, Pr). The Re$=$Ce and Sm members were previously synthesized [1], while their electronic properties have not been reported. We have recently grown single crystals of Re$_{2}$NiGa$_{9}$Ge$_{2}$ (Re$=$Ce, Sm, Pr) and characterized their electronic and magnetic properties. We find all these materials are antiferromagnetic, with T$_{N} \quad =$2.5 K, 5 K, 3.4 K respectively for Re$=$Ce, Pr and Sm. Moreover, they also exhibit large values of electronic specific coefficient: $\gamma \approx $101 mJ mol-Ce$^{-1}$ K$^{-2}$ for Re$=$Ce, 368 mJ mol-Pr$^{-1}$ K$^{-2}$ for Re$=$Pr, and 196.4 mJ mol-Sm$^{-1}$ K$^{-2}$ for Re$=$Sm, indicating enhanced Kondo effect and the presence of AFM Kondo lattice. Our findings suggest that Re$_{2}$NiGa$_{9}$Ge$_{2}$ (Re$=$Ce, Pr, Sm) could be interesting candidate materials for exploring novel exotic properties of correlated electrons through external parameter tuning such as chemical substitution and pressure. Reference: [1] M. A. Zhuravleva and M. G. Kanatzidis, Inorg. Chem. 2008, 47 (20), 9471-9477.