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11The Bushveld Complex in South Africa hosts the world's largest resources of platinum-12 group elements (PGE), which are mainly mined from three ore bodies, namely the Merensky 13Reef, the UG-2 chromitite and the Platreef. In these ores, the PGE are bimodally distributed, 14 occurring both as discrete platinum-group minerals (PGM) and hosted by sulfides. The 15 presence of PGE in sulfides has been demonstrated by electron probe microanalysis, laser 16 ablation induced coupled plasma mass spectrometry, secondary ion mass spectrometry and 17 particle-induced X-ray emission. However, evidence is lacking on the mineralogical siting of 18 the PGE, e.g. whether they occur in solid solution, as nano-and/or micro-inclusions. 19Therefore, in the present study a combination of focused ion beam and transmission electron 20 microscopy was used which allows to obtain crystal-structural relationships between the host 21 mineral and incorporated trace elements and revealing the physicochemical state of the PGE 22 in sulfides. 2The present study confirms the existence of micrometer-sized discrete PGM in the ores. 24Further, the PGE occur in a number of forms, namely (1) as discrete nano-inclusions of PGM, 25(2) as patchily distributed solid solution, (3) ordered within the pentlandite crystal structure, 26 substituting for Ni and/or Fe (superlattice), and (4) as homogenous solid solution. Nanometer-27 sized PGM (nPGM) show no orientation relationship with the host sulfide mineral. 28Consequently, they are discrete phases, which were trapped within pentlandite during sulfide

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