(a) The phonon spectrum of TaSb along the C_3v-symmetric line of the Brillouin zone: doubly degenerate phonon bands (4,5)and (iv,v) can be seen. (b) The phonon spectrum of TaSb with the xx and yy force constants in the dynamical matrix made unequal for Ta. The degeneracy of (4,5) and (iv, v) is lifted. (c) The phonon spectrum of TaSb with the xx and yy force constants in the dynamical matrix made unequal for Sb. The degeneracy of (4,5) and (iv, v) is lifted. (d) The non-topological open nodal line formed in the BZ by bands iv and v of panel (a). The loop S¹ encircles this line, but ϕB(S¹) = 0. (e) The closed nodal loop formed by bands iv and v in the BZ for the case of panel (b) away from the Γ –line. The contour S² links with this loop and ϕB(S²) = π. (f) The closed nodal loop formed by bands iv and v in the BZ for the case of panel (c). For a contour S³ linked with this loop, ϕB(S³) = π. Figure adopted from Ref. [42] with permission.