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Figure 1
(a) Tetragonal ThSi2 and (b) hexagonal AlB2 structures of RSi2 and disordered as well as (c) ordered AlB2-like R2TSi3 compounds (unit cell outline in black). The AlB2 structures form a 2D sublattice of hexagonally arranged Si atoms (red bonds). In contrast, the ThSi2 structures form 3D networks with incomplete hexagons (red bonds), accompanied with the formation of zigzag chains alternately in a and b directions ab direction along the c stacking (orange bonds). |