  Topological nodal-line semimetals (TNLSMs) are characterized by
symmetry-protected band crossings extending along one-dimensional lines in
momentum space. The nodal lines exhibit a variety of possible configurations,
such as nodal ring, nodal link, nodal chain, and nodal knot. Here, using
angle-resolved photoemission spectroscopy, we observe nodal rings in the
orthogonal kz = 0 and kx = 0 planes of the Brillouin zone in TiB2. The nodal
rings connect with each other on the intersecting line {\Gamma}-K of the
orthogonal planes, forming a remarkable nodal-chain structure. Furthermore, we
observe surface states (SSs) on the (001) cleaved surface, which are consistent
with the calculated SSs considering the contribution from both Ti and B
terminations. The calculated SSs have novel Dirac-cone-like band structures,
which are distinct from the usual drumhead SSs with a single flat band proposed
in other TNLSMs.
