  Spin-orbit coupling (SOC) has gained much attention for its rich physical
phenomena and highly promising applications in spintronic devices. The
Rashba-type SOC in systems with inversion symmetry breaking is particularly
attractive for spintronics applications since it allows for flexible
manipulation of spin current by external electric fields. Here, we report the
discovery of a giant anisotropic Rashba-like spin splitting along three
momentum directions (3D Rashba-like spin splitting) with a helical spin
polarization around the M points in the Brillouin zone of trigonal layered
PtBi2. Due to its inversion asymmetry and reduced symmetry at the M point,
Rashba-type as well as Dresselhaus-type SOC cooperatively yield a 3D spin
splitting with alpha~ 4.36 eVA in PtBi2. The experimental realization of 3D
Rashba-like spin splitting not only has fundamental interests but also paves
the way to the future exploration of a new class of material with unprecedented
functionalities for spintronics applications.
