The soft-gamma repeater Swift J1818.0 - 1607 is only the fifth magnetar found to exhibit pulsed radio emission .
Using the Ultra-Wideband Low receiver system of the Parkes radio telescope , we conducted a 3 h observation of Swift J1818.0 - 1607 .
Folding the data at a rotation period of P = 1.363 s , we obtained wideband polarization profiles and flux density measurements covering radio frequencies between 704-4032 MHz .
After measuring , and then correcting for the pulsar ’ s rotation measure of 1442.0 \pm 0.2 rad m ^ { -2 } , we find the radio profile is between 80-100 per cent linearly polarized across the wide observing band , with a small amount of depolarization at low frequencies that we ascribe to scatter broadening .
We also measure a steep spectral index of \alpha = -2.26 ^ { +0.02 } _ { -0.03 } across our large frequency range , a significant deviation from the flat or inverted spectra often associated with radio-loud magnetars .
The steep spectrum and temporal rise in flux density bears some resemblance to the behaviour of the magnetar-like , rotation-powered pulsar PSR J1119 - 6127 .
This leads us to speculate that Swift J1818.0 - 1607 may represent an additional link between rotation-powered pulsars and magnetars .