  Magnetic-field (H) induced first-order magnetic transition and the assiciated
electronic phase-separation phenomena are active topics of research in
magnetism. Magnetoresistance (MR) is a key property to probe these phenomena
and, in literature, a butterfly-shaped MR loop has been noted while cycling the
field, with the envelope curve lying below the virgin curve in MR versus H
plots of such materials. Here, we report an opposite behavior of MR loop for an
alloy, Tb4LuSi3, at low temperatures (<<20 K) in the magnetically ordered
state. Such an anomalous curve reveals unexpected domination of higher
resistive high-field phase in electronic conduction, unlike in other materials
where conducion is naturally by low-resistive high-field phase that follows
first-order transition. The observed features reveal an unusual electronic
phase separation, namely involving high-resistive high-field phase and
low-resistive virgin phase.
