Investigation of new lanthanum-, cerium- and uranium-based ternary intermetallics

Abstract

While searching for new Ce- and U-based “heavy fermion” systems, we have investigated the following intermetallic compounds: CeCu2Ge2, CeCu2Sn2, CeAg2Ge2, CeZn2Al2 (tetragonal ThCr2Si2-structure and modifications thereof); CeRu3Si2, URu3Si2 (hexagonal LaRu3Si2-structure); Ce2Cu7Al10, U2Cu7Al10 (trigonal Th2Mn17-structure); CeCu4Al8, CeAg4Al8, UCu4Al8 (tetragonal CeMn4Al8-structure); LaCu13−xAlx with x = 3, 5.5, and 6.5, as well as CeCu6.5Al6.5 (cubic NaZn13-structure). Resistive and inductive measurements were undertaken between T = 30 mK and room temperature, and two new superconductors were found: LaCu6.5Al6.5 (Tc = 0.65 K) and CeRu3Si2 (Tc = 1.2 K). The specific heat and thermopower of two of these systems have also been measured. CeCu4Al8 shows interesting features that are presumably related to fine structure in the “heavy-fermion” density of states near the Fermi level. CeCu6.5A16.5 shows a magnetic transition at T = 0.5 K which resembles a “spin-glass freezing” rather than a formation of long-range magnetic order