Spin-Orbit Coupling (SOC)

Is it possible to consider Spin-Orbit Coupling in SIESTA?

Spin-Orbit Coupling is included in SIESTA 4.1.

Is spin.orbitstrength necessary for a calculation in siesta?
what should be its value?

We advise you to use the default value (1) for the spin.orbitastrenght.

The value should be changed only if the user knows what he is doing and it concerns usually testing and exploring physics.