Ti2Ni2In, Zr2Co2In, and Zr2Pd2In - Intermetallic Compounds with Ordered U3Si2 and Zr3Al2 Type Structure

Ti:N i2ln, Zr2Co2ln, and Zr^Pd^In were synthesized by reacting the elements in an arcmelting furnace and subsequent annealing at 1070 K. The compounds were investigated by X-ray diffraction on both powders as well as single crystals. Z rC o iIn adopts the ordered UjSi: type structure: P4/mbm, a = 720.54(7), c = 331.59(4) pm. The structure consists of planar [Co2lnj layers with C02 dumb-bells which are separated by the zirconium atoms. Ti2Ni2ln and Z nP d2ln crystallize with the ordered Z riA b type structure (space group P42/mnm), a superstructure of U?Si2: a = 694.3(2), c = 623.2(2) pm for TioNi^In and a = 746.0(1), c = 686.1(1) pm for Zr2Pd2ln. The Ni2 and Pd2 dumb-bells in the Ni2ln and Pd2ln layers of Ti2Ni2In and Z n P ^ In are shifted from the mirror planes of the subcell resulting in puckered layers with weak interlayer Ni-Ni and Pd-Pd contacts, respectively. The indium atoms in these compounds occupy [Tis] and [Zr*] square prisms while the transition metal atoms are surrounded by [Tia] and [Zr6] trigonal prisms. These structural fragments are derived from the CsCl and AIB2 type structures. Chemical bonding in these intermetallic compounds is briefly discussed. Magnetic susceptibility measurements of compact polycrystalline samples indicate Pauli paramagnetism.