  The spectrum of the unidentified infrared (UIR) emission bands between 5.9
and 11.7 [micro]m has been observed for the first time in the disk of an
external galaxy. We have used the low-resolution spectrometer of the ISOPHOT
instrument aboard ISO. The UIR bands at 6.2, 7.7 and 11.3 [micro]m have
absolute intensities which are similar to the values observed for the diffuse
emission of our own Galaxy. The UIR bands between 5.9 and 11.7 [micro]m
contribute ~9% of the total IR radiation of NGC 891. The intensity ratios and
band widths in the NGC 891 disk emissions are similar to the diffuse emission
of the Milky Way, pointing to a common carrier for the UIR bands in the two
galaxies. However, there are some notable variations of the band ratios along
the major axis of the galaxy.
