In previous work we showed that bright atomic solitons can arise in spinor
Bose-Einstein condensates in the form of gap solitons even for repulsive ma
ny-body interactions. Here we further explore the properties of atomic gap
solitons and show that their internal structure can be used to both excite
them and control their centre-of-mass motion using applied laser and magnet
ic fields. As an illustration we demonstrate a nonlinear atom-optical Mach-
Zehnder interferometer based on gap solitons.