Ternary rare-earth aluminium intermetallics RETAl (RE = Y, Ho, Tm, Lu; T = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) with an ordered anti-CoAl structure.

Twenty new rare-earth metal rich intermetallic aluminium compounds, RETAl (RE = Y, Ho, Tm, Lu; T = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt), were synthesized by arc melting the elements. The compounds crystallize, in analogy to e.g. the respective Cd representatives, with a ternary ordered structure as anti-type to the hexagonal CoAl type, with the space group P6/mmc. The three crystallographically independent rare-earth metal sites occupy the aluminium positions of the aristotype, while the transition metal and aluminium atoms are ordered on the two cobalt sites. Like other rare-earth rich compounds the RETX members also exhibit transition-metal-centred T@RE trigonal prisms as striking structural building units. The prepared compounds have been investigated by susceptibility measurements and Al solid-state MAS-NMR measurements conducted on the Pauli-paramagnetic Y and Lu compounds. Some compounds show a certain amount of disorder as seen from the single crystal structure analysis and from signal broadening in the NMR investigations. By separating Knight shifts from second-order quadrupolar shifts via field dependent measurements, monotonic trends can be discerned regarding the effect of the T atom valence electron concentration and period number, as well as the effect of the closed 4f shell contributed in the Lu compounds. The results confirm that a comparison of Knight shifts within a series of isotypic compounds can reveal important electronic structure information in intermetallic systems.