“…However, there are several nonoxide perovskite materials that host a transition-metal ion in the place of oxygen at the face-center lattice sites of the cubic unit cell, and these are usually referred to as metallic perovskites. MgCNi 3 [3], RhFe 3 N [4,5], Sc 3 MC (M = Al, Ga, In, Tl) [6], Mn 3 GaC [7][8][9], and RT 3 X (R = rare earth ion; T = Pd, Rh; X = B, C) [10][11][12][13][14][15][16][17][18] are some of the noted metallic perovskites that have been thoroughly investigated and several exciting properties such as superconductivity, giant magnetoresistance, anomalous thermal expansion, magnetocaloric effect, tunable valence behavior, and temperature-independent electrical resistivity have been observed. Interestingly, several binary RT 3 compounds related to the RT 3 X perovskites also crystallize in the structurally related cubic AuCu 3 phase, where the body-center site remains vacant [19][20][21][22][23].…”