  We report the discovery by XMM-Newton and Chandra of a hard extended X-ray
source (XMM J174540-2904.5) associated with a compact non-thermal radio
filament (the Sgr A-E `wisp'=1LC 359.888-0.086= G359.88-0.07), which is located
within ~4 arcmin of the Galactic Centre. The source position is also coincident
with the peak of the molecular cloud, M -0.13-0.08 (the `20 km/s' cloud). The
X-ray spectrum is non-thermal with an energy index of 1.0 (+1.1 -0.9) and
column density of 38 (+7 -11) x 10^22 H/cm2. The observed 2--10 keV flux of 4 x
10^-13 erg/s/cm2 converts to an unabsorbed X-ray luminosity of 1 x 10^34 erg/s
assuming a distance of 8.0 kpc. The high column density strongly suggests that
this source is located in or behind the Galactic Centre Region. Taking account
of the broad-band spectrum, as well as the source morphology and the positional
coincidence with a molecular cloud, we concluded that both the radio and X-ray
emission are the result of synchrotron radiation. This is the first time a
filamentary structure in the Galactic Centre Region. has been shown,
unequivocally, to have a non-thermal X-ray spectrum.
