We have carried out observations of the newly-discovered magnetar in the direction of Sagittarius A ^ { * } using the Australia Telescope Compact Array in four frequency bands from 4.5 to 20 GHz .
Radio pulsations are clearly detected at all frequencies .
We measure the pulsar ’ s dispersion measure to be 1650 \pm 50 cm ^ { -3 } pc , the highest of any of the known pulsars .
Once Faraday rotation has been taken into account , the pulse profile is more than 80 % linearly polarized at all frequencies and has a small degree ( 5 % ) of circular polarization .
The rotation measure of -67000 \pm 500 rad m ^ { -2 } is the largest ( in magnitude ) ever measured for a pulsar but still a factor 8 smaller than Sgr A ^ { * } itself .
The combination of the dispersion and rotation measures implies an integrated magnetic field strength of -50 \mu G along the line of sight .
The flux density appears to have increased by about a factor of two between observations made 30 days apart .
This object therefore joins the small class of radio emitting magnetars .