Impedance and specific heat of RM4Al8 and RAg6In6 compounds

The results of experimental investigations of the temperature dependences of the surface resistance and specific heat of ternary rare-earth compounds are presented: LuFe4Al8, ScFe4Al8, CeFe4Al8, CeCr4Al8, YFe4Al8, YCr4Al8, YMn4Al8, UCu4Al8, LaAg6In6, and PrAg6In6, which have ThMn12 structure. It is shown that at a certain temperature, characteristic for each compound with Fe, Cr, and Mn, below the Neel temperature a jump is observed in the total impedance and specific heat. At lower temperatures a negative magnetoresistance is observed in these compounds in weak magnetic fields. Superconducting phases are found in the compounds ScFe4Al8 (Tc=6 K), YCr4Al8 (Tc=4.5 K), YFe4Al8 (Tc=6 K), and PrAg6In6 (Tc=8.3 K).