  We present a magneto-infrared spectroscopic study of thin Bi2Se3 single
crystal flakes. Magneto-infrared transmittance and reflectance measurements are
performed in the Faraday geometry at 4.2K in a magnetic field up to 17.5T. Thin
Bi2Se3 flakes (much less than 1{\mu}m thick) are stabilized on the Scotch tape,
and the reduced thickness enables us to obtain appreciable far-infrared
transmission through the highly reflective Bi2Se3 single crystals. A pronounced
electron-phonon coupling is manifested as a Fano resonance at the {\alpha}
optical phonon mode in Bi2Se3, resulting from the quantum interference between
the optical phonon mode and the continuum of the electronic states. However,
the Fano resonance exhibits no systematic line broadening, in contrast to the
earlier observation of a similar Fano resonance in Bi2Se3 using
magneto-infrared reflectance spectroscopy.
