  A complete overview of the supernova remnant (SNR) population is required to
investigate their evolution and interaction with the surrounding interstellar
medium in the Small Magellanic Cloud (SMC). Recent XMM-Newton observations of
the SMC cover three known SNRs (DEM S5, SNR B0050-72.8, and SNR B0058-71.8),
which are poorly studied and are X-ray faint. We used new multi-frequency
radio-continuum surveys and new optical observations at Ha, [SII], and [OIII]
wavelengths, in combination with the X-ray data, to investigate their
properties and to search for new SNRs in the SMC. We used X-ray source
selection criteria and found one SMC object with typical SNR characteristics
(HFPK 334), that was initially detected by ROSAT. We analysed the X-ray spectra
and present multi-wavelength morphological studies of the three SNRs and the
new candidate. Using a non-equilibrium ionisation collisional plasma model, we
find temperatures kT around 0.18 keV for the three known remnants and 0.69 keV
for the candidate. The low temperature, low surface brightness, and large
extent of the three remnants indicates relatively large ages. The emission from
the new candidate (HFPK 334) is more centrally peaked and the higher
temperature suggests a younger remnant. Our new radio images indicate that a
pulsar wind nebulae (PWN) is possibly associated with this object. The SNRs
known in the SMC show a variety of morphological structures that are relatively
uncorrelated in the different wavelength bands, probably caused by the
different conditions in the surrounding medium with which the remnant
interacts.
