  We report on a recent bright outburst from the new X-ray binary transient
MAXI J1631-479, observed in January 2019. In particular, we present the 30-200
keV analysis of spectral transitions observed with INTEGRAL/IBIS during its
Galactic Plane monitoring program. In the MAXI and BAT monitoring period, we
observed two different spectral transitions between the high/soft and low/hard
states. The INTEGRAL spectrum from data taken soon before the second
transition, is best described by a Comptonised thermal component with an
electron temperature of 30 keV and a high luminosity value of 3x10^38 erg/s in
2-200 keV energy range (assuming a distance of 8 kpc). During the second
transition, the source shows a hard, power-law spectrum. The lack of high
energy cut-off indicates that the hard X-ray spectrum from MAXI J1631-479 is
due to a non-thermal emission. Inverse Compton scattering of soft X-ray photons
from a non-thermal or hybrid thermal/non-thermal electron distribution can
explain the observed X-ray spectrum although a contribution to the hard X-ray
emission from a jet cannot be determined at this stage. The outburst evolution
in the hardness-intensity diagram, the spectral characteristics and the rise
and decay times of the outburst are suggesting this system is a black hole
candidate.
