| Summary: | Several ternary rare-earth metals containing titanium aluminum intermetallics in the <i>RE</i><sub>2</sub>TiAl<sub>3</sub> series (<i>RE</i> = Y, Gd–Lu) have been synthesized from the elements using arc-melting techniques. All compounds crystallize in the trigonal crystal system with rhombohedral space group <i>R</i><span style="text-decoration: overline;">3</span><i>m</i> (<i>Z</i> = 3) and lattice parameters ranging between <i>a</i> = 582–570 and <i>c</i> = 1353–1358 pm. They adopt the Mg<sub>2</sub>Ni<sub>3</sub>Si-type structure, which is an ordered superstructure of the cubic Laves phase MgCu<sub>2</sub> and has been observed for Al intermetallics for the first time. Tetrahedral [TiAl<sub>3</sub>] entities that are connected over all corners form a network where the empty [TiAl<sub>3</sub>] tetrahedra exhibit a full Ti/Al ordering based on the single crystal results. The Al atoms are arranged into 6<sup>3</sup> Kagomé nets, while the Ti atoms connect these nets over the triangular units. In the cavities of this three-dimensional arrangement, the <i>RE</i> cations can be found forming a distorted diamond-type substructure. Magnetic measurements revealed that Y<sub>2</sub>TiAl<sub>3</sub> and Lu<sub>2</sub>TiAl<sub>3</sub> are Pauli paramagnetic substances, in line with the metallic character. The other compounds exhibit paramagnetism with antiferromagnetic ordering at a maximum Néel temperature of <i>T</i><sub>N</sub> = 26.1(1) K for Gd<sub>2</sub>TiAl<sub>3</sub>.
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