Xavier joined the Hierakonpolis Expedition in 2003 and is now a senior member and assistant field director. He has excavated at several localities around the site (Nubian Cemetery HK27C, Khasekhemwy's enclosure, production center HK11C), but it is his experience at the Elite Cemetery HK6 that is more closely related to his research interest. There since 2005, Xavier has taken part in the excavation of the earliest known above-ground funerary architecture in Egypt and of many of the remarkable burials found there. In 2011 and 2012, he kept busy digging out the vast cattle burial known as Tomb 49, but his most significant find, in 2014, was the human burial Tomb 72 that still contained a large part of its assemblage in situ. He also undertook his own excavation project on the Eastern expansion of cemetery HK6 thanks to support from the Schiff-Giorgini Foundation.
In Sudan, Xavier is the co-director of the Swiss-French-Sudanese mission at Kerma - Dokki Gel together with Séverine Marchi. He has been heavily involved with archaeological fieldwork at the site since 2018, where he has taken part in the excavation of one of the largest known ancient town site, where African and Egyptian architectures meet. Earlier, he had collaborated with the British Museum expedition to Sudan, directed by W. Vivian Davies on two projects, one based at the Khartoum National Museum to reconstruct and conserve fragmented New Kingdom granite statuary, the other to record New Kingdom pharaonic rock inscriptions at a number of places along the Nile Valley, including Tombos and Kurgus.
When not in the field, Xavier is the curator of the collection of Egyptian archaeology at the Fondation Gandur pour l'Art in Geneva. He also serves as an Academic Fellow at the University of Geneva's Faculty of Sciences, where he works with the team of the Archaeology of Africa & Anthropology Laboratory (ARCAN). He is the initiator and principal editor of the www.ponda.org web platform dedicated to the documentation of predynastic material culture. This project was generously supported by the Heagy Foundation in 2023.
A Swiss graduate of the University of Geneva (Licence ès Lettres, 2005), Xavier benefited from a full scholarship from the Berrow Fondation and wrote his doctoral dissertation at the University of Oxford on Riverine and desert animals in predynastic Upper Egypt: material culture and faunal remains (available online; graduated 2015), working with Professor John Baines and Dr Renée Friedman.
Xavier also worked in several museums, on temporary exhibitions and permanent displays as well as larger projects. In Geneva, he worked at the Museum of Art and History, where he participated in organising and displaying two temporary exhibitions (Voyages dans l’Antiquité au 20e siècle ; Égypte) and preparing for the current permanent display of the galleries. In Oxford, between 2010 and 2012, Xavier took part in the redevelopment of the Egyptian galleries of the Ashmolean Museum in Oxford, which now prominently display early Egypt material, including its star objects from Hierakonpolis' Main Deposit. He also has experience working at the Musée Gruérien (Switzerland) and the Aga Khan Museum (Toronto).
In addition to his authorship of several articles on Predynastic Egypt, Xavier is the collaborating editor of the recently published volume by A. Loprieno (ed.), in collaboration with X. Droux. Life Histories of Theban Tombs: transdisciplinary investigations of a cluster of rock-cut tombs at Sheikh ‘Abd el-Qurna; he is also assisting in the preparation of R. Friedman (ed.) & X. Droux (coll.): The Nubian cemetery HK27C at Hierakonpolis: final excavation report, Griffith Institute Publications 1, Oxford.