Title:The Puzzle of Meteoritic Minerals Heideite and Brezinaite; Are they Iron-based Superconductors? Are they Technosignatures?

Abstract:Transition metal sulfides (Fe, V)3S4 and (Fe, Ti)3S4, with the monoclinic Cr3S4 type structure have been studied for a long time, itinerant magnetism in form of Spin density waves (SDW) have been found in these systems with different features as evidenced by 57Fe Mossbauer Spectroscopy, there is an intricate relationship between the proportion of Fe, V and Ti atoms, the degree of commensurability of the SDW and the magnetic transition temperature. These sulfides have no natural occurrence on Earth and some of these phases were detected as minerals in meteorites; the mineral Heideite in the Bustee and Kaidun meteorites, with minor proportion of Cr atoms leading to the general formula (Fe, Cr)1+x (Ti, Fe)2S4, and the mineral Brezinaite in the Tucson meteorite, with minor proportion of Fe atoms and traces of V, Ti and Mn atoms, leading to the formula (Cr2.65Fe0.20V0.09Ti0.06Mn0.04)3.04S4. In this critical review of the experimental literature, we discuss the issues that these meteoritic minerals are structurally sensitive to the method of synthesis, and so is their magnetic behavior, especially in the presence of minor and trace elements. This discussion could shed light on our knowledge in Solid State Physics and Planetary Science; these meteoritic minerals are promising candidates for iron-based superconductors because of three clues: they are layered structures, they undergo a transition to SDW with variable degree of commensurability and the minor and trace elements could act as dopants and hence suppress the SDW giving rise to superconductivity. On the other side, the genesis of these meteoritic minerals could require controlled and sophisticated process not easily found in nature. So, it is important to be open-minded and even provocative to consider the following question: Are these meteoritic minerals samples of Extraterrestrial Technosignatures?