SYNTHESIS, CRYSTAL-CHEMISTRY, AND PHYSICAL-PROPERTIES OF TERNARY INTERMETALLIC COMPOUNDS AN(2)T(2)X (AN = PU, AM X = IN, SN, T = CO, IR, NI, PD, PT, RH)

The synthesis, structural, and physical characterization of nine new t ernary intermetallic compounds belonging to the isostructural An(2)T(2 )X family with the transuranium Pu and Am elements, namely, Pu2Ni2In, Pu2Pd2In, Pu2Pt2In, Pu2Rh2In, Pu2Ni2Sn, Pu,Pd,Sn, Pu,Pt,Sn, Am,Ni,Sn, and Am,Pd,Sn, are reported. From these compounds only Pu,Rh,In, Am,Ni, Sn, and Am2Pd2Sn melt incongruently. All of these compounds crystalliz e in a tetragonal U3Si2-type structure, with the space group P4/mbm, ( Z = 2) as most of the U and Np 2-2-1 compounds already found. In this structure, An atoms occupy the 4h (x(1), x(1) + 0.5, 0.5), T the 4g (x (2), x(2) + 0.5, 0), and X the 2a (0, 0, 0) positions. The average val ues of x(1) and x(2) are, respectively, 0.17 and 0.37. Single-crystal X-ray data were refined to R/R-w = 0.045/0.066, 0.033/0.072, 0.066/0.0 80, 0.07010.098, 0.029/0.048, 0.055/0.080, 0.073/0.096, 0.048/0.086, 0 .048/0.065 for Pu2Ni2In, Pu2Pd2In, Pu2Pt2In, Pu2Rh2In, Pu2Ni2Sn, Pu2Pd 2Sn, Pu2Pt2Sn, Am2Ni2Sn, and Am2Pd2Sn, respectively, for seven variabl es. The variation of the lattice parameters and the range of stability of the 2-2-1 phase are discussed in terms of the substitution of diff erent An (actinide), T (transition metal), and X (p-electron) elements in their crystal structure. The possible role of spin fluctuations in the low-temperature behavior of the Pu samples is indicated by magnet ic and electrical resistivity measurements. (C) 1997 Academic Press.