I wonder why you should be interested in the 4f electrons of Bi in the context of band structure. They are deeply embedded within the atom, with a mean square radius of the order 0.5 Bohr radii, and completely insensitive to the chemical environment except for a possible electrostatic shift, if the neighbours are charged. Their binding energy of the order of 160 eV makes them deep core states. The next higher (5d) states have a binding energy of the order of 25 eV and a mean square radius of around 1.3 Bohr radii, and are still not chemically relevant. The 6s and 6p states, on the other hand, have extensions between roughly 2.5 and 3.5 Bohr radii and will be responsible for the formation of bands.