  FeSi is a curious example of a $d$-electron system that manifests many of the
same phenomena associated with $f$-electron Kondo insulators, including
conducting surface states with potentially non-trivial topology. Here we
investigate the magnetization and magnetotransport of these surface states and
how a 2D ferromagnetic state at the surface of FeSi influences the surface
conductivity. We confirm the 2D ferromagnetism via a systematic study of
magnetization on groups of filtered fragments with increasing surface
area-to-volume ratios, identifying characteristic temperatures and magnetic
fields associated with the ordered state. The paramagnetic to ferromagnetic
transition appears broadened, suggesting disorder, which allows spin
fluctuations to manifest up to at least 9 T at 2 K. This highlights the need to
understand the relation between the disorder of the 2D ferromagnetism and the
surface conductivity in FeSi.
