  We show that spinors propagating in curved gravitational background acquire
an interaction with spacetime curvature, which leads to a quantum mechanical
geometric effect. This is similar to what happens in the case of magnetic
fields, known as Pancharatnam-Berry phase. As the magnetic and gravitational
fields have certain similar properties, e.g. both contribute to curvature, this
result is not difficult to understand. Interestingly, while spacetime around a
rotating black hole offers Aharonov-Bohm and Pancharatnam-Berry both kinds of
geometric effect, a static spacetime offers only the latter. In the bath of
primordial black holes, such gravity induced effects could easily be measured
due to their smaller radius.
