Single crystal, bulk Si1-xGex alloys are available across the alloy composition range, and provide opportunity for study of alloy properties in transition between the two elements. In particular, implanted muons acting as hydrogen analogues enable properties of hydrogen defect states to be determined to aid our understanding of the behaviour of this important impurity. Specifically, a simple band alignment model predicts that the ionisation behaviour of the bond-centred and tetrahedral muonium species should show interesting features for high-Ge alloys. Previous RF and high-TF measurements have enabled the behaviour of these muonium states to be observed, but the precise mechanisms for their disappearance with temperature are still not clear. We propose to use RF-mSR observations of diamagnetic and neutral states to clarify these processes in several high-Ge alloy samples