  The Majorana zero mode (MZM), which manifests as an exotic neutral excitation
in superconductors, is the building block of topological quantum computing. It
has recently been found in the vortices of several iron-based superconductors
as a zero-bias conductance peak (ZBCP) in tunneling spectroscopy. In
particular, a clean and robust MZM has been observed in the cores of free
vortices in (Li0.84Fe0.16)OHFeSe. Here using scanning tunneling spectroscopy
(STS), we demonstrate that Majorana-induced resonant Andreev reflection occurs
between the STM tip and this zero-bias bound state, and consequently, the
conductance at zero bias is quantized as 2e2/h. Our results present a hallmark
signature of the MZM in the vortex of an intrinsic topological superconductor,
together with its intriguing behavior.
