Electron-Precise/Deficient La₅_-<i>_x</i>Ca<i>_x</i>Ge₄ (3.4 ≤ <i>x</i> ≤ 3.8) and Ce₅_-<i>_x</i>Ca<i>_x</i>Ge₄ (3.0 ≤ <i>x</i> ≤ 3.3): Probing Low-Valence Electron Concentrations in Metal-Rich

We report for the first time the syntheses of electron-precise/deficient alloys, Ln5-xCaxGe4 (Ln = La, Ce; x = 3.37, 3.66, 3.82 for La; x = 3.00, 3.20, 3.26 for Ce), in the metal-rich R5Tt4 Zintl system (R = rare earth metal; Tt = Si, Ge). The new alloys extend the phase width from electron-rich to open-shell electron-deficient region in the metal-rich Zintl system and demonstrate possible occurrence of varied electron deficiencies in Zintl phases without structural changes, as a result of other existing structure-forming factors.