  Dirac nodal line semimetals represent a new state of quantum matters in which
the electronic bands touch to form a closed loop with linear dispersion. Here,
we report a combined study on ZrSiS by density functional theory calculation,
scanning tunneling microscope (STM) and magneto-transport measurements. Our STM
measurements reveal the spectroscopic signatures of a diamond-shaped Dirac bulk
band and a surface band on two types of cleaved surfaces as well as a spin
polarized surface band at ${\bar{\Gamma}}$ at E~0.6eV on S-surface, consistent
with our band calculation. Furthermore, we find the surface termination does
not affect the surface spectral weight from the Dirac bulk bands but greatly
affect the surface bands due to the change in the surface orbital composition.
From our magneto-transport measurements, the primary Shubnikov de-Haas
frequency is identified to stem from the hole-type quasi-two-dimensional Fermi
surface between {\Gamma} and X. The extracted non-orbital magnetoresistance
(MR) contribution D($\theta$, H) yields a nearly H-linear dependence, which is
attributed to the intrinsic MR in ZrSiS. Our results demonstrate the unique
Dirac line nodes phase and the dominating role of Zr-d orbital on the
electronic structure in ZrSiS and the related compounds.

Materials Science