  We argue that certain (semi)conductors should exhibit asymmetry of their
mechanical and conducting properties with respect to clockwise/counterclockwise
rotation. We show that a cylinder made of a suitably chosen semiconductor
coated in a metallic film and placed in the magnetic-field background can serve
as a "rotational diode" which conducts electricity only at a specific range of
angular frequencies. The critical angular frequency and the direction of
rotation can be tuned with the magnetic field's strength. Mechanically, the
rotational diode possesses different moments of inertia when rotated in
clockwise and counterclockwise directions.
