  Type-II nodal line semimetal (NLS) is a new quantum state hosting
one-dimensional closed loops formed by the crossing of two bands which have the
same sign in their slopes along the radial direction of the loop. According to
the theoretical prediction, Mg3Bi2 is an ideal candidate for studying the
type-II NLS by tuning its spin-orbit coupling (SOC). In this paper, high
quality Mg3Bi2 films are grown by molecular beam epitaxy (MBE). By in-situ
angle resolved photoemission spectroscopy (ARPES), a pair of surface resonance
bands (SRBs) around Gamma point is clearly seen. It shows that Mg3Bi2 films
grown by MBE is Mg(1)-terminated by comparing the ARPES data with the first
principles calculations results. And, the temperature dependent weak
anti-localization (WAL) effect in Mg3Bi2 films is observed under low magnetic
field, which shows a clear two dimensional (2D) e-e scattering characteristics
by fitting with the Hikami-Larkin-Nagaoka (HLN) model. Combining with ARPES,
magneto-transport measurements and the first principles calculations, this work
proves that Mg3Bi2 is a semimetal with topological surface states TSSs, which
paves the way for Mg3Bi2 as an ideal materials platform for studying the exotic
features of type-II nodal line semimetals (NLSs) and the topological phase
transition by tuning its SOC.
