Abstract
Using Electron Paramagnetic Resonance, it has been shown that a static magnetic field perpendicular to the easy magnetization axis of an AcMn12 molecule could increase the tunneling effect. In practice, the static magnetic field cannot be strictly perpendicular to the easy axis, a slight component parallel to this axis remains. Here, it is shown that this component can change completely the shape of the line. This behaviour is due to a non-constant coupling coefficient, which is calculated here. Then, experimental data are compared to these predictions, and good agreement is obtained.