During the last few years superconductive systems of heavy fermions with highly large values ofm* and electronic heat capacityγT have been thoroughly investigated.
The following compounds viz CeCu2Si2 (Tc=0.6 K;γ=1100*), UBe13(Tc=0.95 K;γ=1000) and UPt3 (Tc=0.5 K;γ=450)(I) may be referred to such systems as well as the U and Ce compounds: U2Pt C2 (Tc=1.47 K;γ=75), U6Fe (Tc=3.86 K;γ=25), U6Co (Tc=2.3 K;γ=21), URu2Si2 (Tc=0.68 K,γ=17.6), as well asα-U (Tc=2.1;γ=12), CeRu3Si2 (Tc=1 K;γ=39), CeOs2 (Tc=1,1 K;γ=22), CeRu2 (Tc=6 K;γ=23.3) and α-Ce (Tc≲2K;γ=14) (Alekseevskii and Homskiy 1985).
It should be noted that there exists a class of U and Ce compounds with a similar structure as those given above, which undergo transition to superconductive state, but are not characterized by abnormal values ofm* (Alekseevskii 1984).
Many authors considered superconductivity of heavy fermion systems as unusually anisotropic where charge carrier coupling occurs in P-state (Stewart 1984). On the other hand such a view does not agree with many experimental results, e.g. lack of anisotropy Hc2 for UBe13 (Alekseevskiiet al 1985) as predicted by Gorkov (1984) and the results of investigation of the Josephson effect. The Hall-effect investigations for UBe13 in a wide range of fields and temperatures (Alekseevskii 1984) make it possible to consider systems with two types of carriers—heavy and light. The unique properties of the above systems in a number of cases are possibly caused by these two types of carriers and the peculiarity of interaction between them.