Symmetry‐Breaking Transitions in HoCuAs2–xPx and ErCuAs2–xPx (x = 0–2): Crystal Structure, Application of Landau Theory, Magnetic and Electrical Properties

Crystal structures of compounds undergoing symmetry‐breaking transitions have been investigated by the X‐ray single crystal and powder methods. While the phases HoCuAs2 through HoCuAs1.33P0.67 and ErCuAs2 through ErCuAsP retain the tetragonal HfCuSi2 structure (P4/nmm space group), the compounds HoCuAsP through HoCuAs0.33P1.67 and ErCuAs0.67P1.33 through ErCuAs0.33P1.67 undergo orthorhombic distortions to the GdCuAs1.15P0.85 structure (Pmmn …