  The discovery of superconductivity in pnictides and iron chalcogenides
inspires the search for new iron based superconducting phases. Iron-rich
meteorites present a unique opportunity for this search, because they contain a
broad range of compounds produced under extreme growth conditions. We
investigated a natural iron sulfide based materials (Troilite) inclusion with
its associated minerals in the iron meteorite Tlacotepec. Tlacotepec formed in
an asteroidal core under high pressure and at high temperature over millions of
years, while insoluble sulfur rich materials segregated into inclusions during
cooling along with included minerals. The search for superconductivity in these
heterogeneous materials requires a technique capable of detecting minute
amounts of a superconducting phase embedded in a non-superconducting matrix. We
used Magnetic Field Modulated Microwave Spectroscopy (MFMMS), a very sensitive,
selective, and non-destructive technique, to search for superconductivity in
heterogeneous systems. Here, we report the observation of an electro-magnetic
phase transition at 117 K that causes a MFMMS-response typical of a
superconductor. A pronounced and reproducible peak together with isothermal
magnetic field sweeps prove the appearance of a new electromagnetic phase below
117 K. This is very similar to the characteristic response due to flux trapping
in a granular superconductor with a short coherence length. Although the
compound responsible for the peak in the MFMMS-spectra was not identified, it
is possibly an iron sulfide based phase, or another material heterogeneously
distributed over the inclusion.
