  We report the study of a tri-axial vector magnetoresistance (MR) in
nonmagnetic (Bi1-xInx)2Se3 nanodevices at the composition of x = 0.08. We show
a dumbbell-shaped in-plane negative MR up to room temperature as well as a
large out-of-plane positive MR. MR at three directions is about in a -3%: -1%:
225% ratio at 2 K. Through both the thickness and composition-dependent
magnetotransport measurements, we show that the in-plane negative MR is due to
the topological phase transition enhanced intersurface coupling near the
topological critical point. Our devices suggest the great potential for
room-temperature spintronic applications, for example, vector magnetic sensors.
