Topological Dirac and Weyl semimetals are currently attracting intense interest due to their exotic physical properties. Transition metal diarsenides such as ${\mathrm{MoAs}}_2$ and ${\mathrm{WAs}}_2$ have been reported to harbor very high magnetoresistance suggesting the possible existence of a topological quantum state, although this conclusion remains dubious. Here, using systematic angle-resolved photoemission spectroscopy (ARPES) measurements and parallel first-principles calculations, we discuss the electronic structures of ${\mathrm{TAs}}_2$ (T = Mo, W). Two different cleavage planes of ${\mathrm{MoAs}}_2$ are found to harbor distinctly different surface states. Our experiments show the presence of Dirac-like dispersions on the (001) plane, which our first-principles calculations ascribe to trivial surface states. Our in-depth study also finds ${\mathrm{WAs}}_2$ to possess a trivial electronic structure. Our study emphasizes the importance of identifying the cleavage plane in low-symmetry systems and indicates that topological semimetallic states are not the key for generating high magnetoresistance in ${\mathrm{MoAs}}_2$ and ${\mathrm{WAs}}_2$.

• Received 16 January 2020
• Accepted 21 April 2021

DOI:https://doi.org/10.1103/PhysRevResearch.3.023170

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Published by the American Physical Society