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 Néel 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).

Temperature dependences of low-frequency impedance (0–107 Hz) and heat capacity of LuFe4Al8 are studied at low temperature in the intervals 4.5–300 K and 1.5–120 K, respectively. The observed singularities suggest that antiferromagnetic phase ordering occurs at TN=100.5 K. A sharp increase in the resistance is observed at a certain temperature T1<TN below which a negative magnetoresistive effect is detected in a weak magnetic field (H<50 Oe). It is shown that the low- temperature anomalies at T<25 K are associated with the superconducting transition. This is supported by the presence of the Meissner effect, levitation, a decrease in ohmic losses, as well as the influence of a static magnetic field and direct current on the resistance of the compound. A magnetostructural phase transition, which is assumed to occur at T1<TN, may be responsible for the peculiarities observed in the physical properties of LuFe4Al8.

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The temperature dependence and concentration dependence of the heat capacity C and surface resistance Rs are measured in the compounds YNi5−xCux (x=0, 0.1, 0.2, 0.25, 0.6, and 1.25). The measured values of C(x) and Rs(x) are used to determine the concentration dependence of the density of states N(E,x). A maximum is observed on N(E,x) at x=0.2. The results constitute direct experimental confirmation of the nonmonotonic dependence of N(E,x) that has previously been predicted theoretically. It is found that at certain values of x the low-temperature heat capacity of the compounds YNi5−xCux increases with decreasing temperature, and the temperature dependence of the electrical resistance has a minimum at T=10 K. Below 10 K the temperature dependence of the resistance obeys a logarithmic law.