Context :

Aims : The supernova remnant ( SNR ) G15.4+0.1 is considered to be the possible counterpart of the \gamma -ray source HESS J1818 - 154 .
With the goal of getting a complete view of this remnant and understanding the nature of the \gamma -ray flux , we conducted a detailed radio study that includes the search for pulsations and a model of the broadband emission for the SNR G15.4+0.1/HESS J1818 - 154 system .

Methods : Low-frequency imaging at 624 MHz and pulsar observations at 624 and 1404 MHz towards G15.4+0.1 were carried out with the Giant Metrewave Radio Telescope ( GMRT ) .
We correlated the new radio data with observations of the source at X-ray and infrared wavelengths from XMM-Newton and Herschel observatories , respectively .
To characterize the neutral hydrogen ( HI ) medium towards G15.4+0.1 , we used data from the Southern Galactic Plane Survey .
We modelled the spectral energy distribution ( SED ) using both hadronic and leptonic scenarios .

Results : From the combination of the new GMRT observations with existing data , we derived a continuum spectral index \alpha = -0.62 \pm 0.03 for the whole remnant .
The local synchrotron spectra of G15.4+0.1 , calculated from the combination of the GMRT data with 330 MHz observations from the Very Large Array , tends to be flatter in the central part of the remnant , accompanying the region where the blast wave is impinging molecular gas .
No spectral index trace was found indicating the radio counterpart to the pulsar wind nebula proposed from X-ray observations .
In addition , the search for radio pulsations yielded negative results .
Emission at far-infrared wavelengths is observed in the region where the SNR shock is interacting with dense molecular clumps .
We also identified HI features forming a shell that wraps most of the outer border of G15.4+0.1 .
Characteristic parameters were estimated for the shocked HI gas .
We found that either a purely hadronic or leptonic model is compatible with the broadband emission known so far .

Conclusions :