Topological phase transitions without symmetry indication in NaZnSb[Formula: see text] Bi[Formula: see text]

We study topological phase transitions in tetragonal NaZnSb[Formula: see text] Bi[Formula: see text] , driven by the chemical composition x. Notably, we examine mirror Chern numbers that change without symmetry indicators. First-principles calculations are performed to show that NaZnSb[Formula: see text] Bi[Formula: see text] experiences consecutive topological phase transitions, diagnosed by the strong [Formula: see text] topological index [Formula: see text] and two mirror Chern numbers [Formula: see text] and [Formula: see text] . As the chemical composition x increases, the topological invariants ([Formula: see text] ) change from (000), (020), (220), to (111) at x = 0.15, 0.20, and 0.53, respectively. A simplified low-energy effective model is developed to examine the mirror Chern number changes, highlighting the central role of spectator Dirac fermions in avoiding symmetry indicators. Our findings suggest that NaZnSb[Formula: see text] Bi[Formula: see text] can be an exciting testbed for exploring the interplay between the topology and symmetry.