  We introduce a formalism to compute the neutron magnetic form factor Fm(q)
within a first-principles Density Functional Theory (DFT) + Dynamical Mean
Field Theory (DMFT). The approach treats spin and orbital interactions on the
same footing and reduces to earlier methods in the fully localized or the fully
itinerant limit. We test the method on various actinides of current interest
NpCoGa5, PuSb and PuCoGa5; we show that PuCoGa5 is in mixed valent state, which
naturally explains the measured magnetic form factor.
