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Figure 2: (a) Nodal line (in red) in the BZ and its projection on the (001), (010), and (100) planes (in grey). The parameters are set as , , , , , and . (b) Band structure along , where A and B are two points with on the nodal line as labeled in (a). (c) The band dispersions with the surface states (red colour lines) on the (001) surface. The drumhead-like surface states are nestled inside the projection of the nodal ring. (d) The Berry phase equals for inside the nodal ring, while it is zero for outside the nodal ring.