Compared to inversion-symmetric systems, the emerging bulk Dirac point (DP) in noncentrosymmetric systems is much harder and its symmetry-protection mechanism is poorly understood. In this Rapid Communication, we propose that orthogonal glide symmetries can protect two distinct types of bulk anisotropic DPs. One is the ordinary anisotropic DP that is doubly degenerate only along one invariant axis, which results from symmetry-protected accidental band crossing. The other one is a symmetry-enforced DP fixed at a non-time-reversal-invariant point, which is doubly degenerate at three orthogonal directions. This unique topological phase is exemplified by ${\mathrm{KSnSe}}_2$ in space group 108. Our work not only unveils a unique symmetry-protection mechanism but also provides a material candidate for exploring multitype Dirac fermions in noncentrosymmetric systems.

中文翻译：

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非中心对称系统中受正交滑移对称性保护的多型狄拉克费米子

与反对称系统相比，非中心对称系统中新兴的本体狄拉克点（DP）更加困难，并且其对称保护机制也知之甚少。在本快速通信中，我们提出正交滑翔对称性可以保护两种不同类型的体各向异性DP。一种是普通各向异性DP，它仅沿一个不变轴双重退化，这是由对称保护的偶然带交叉引起的。另一个是固定在非时间反转不变点上的对称增强DP，它在三个正交方向上双重退化。这个独特的拓扑阶段的示例是${\mathrm{硒化钾}}_2$ 在空间群108中。我们的工作不仅揭示了独特的对称保护机制，而且还为探索非中心对称系统中的多型狄拉克费米子提供了重要的材料。