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We present the N-band (8-13 micron) spectrum of the hidden compact radiosuper-star cluster in NGC 5253, C2, obtained with TIMMI2 on the ESO 3.6mtelescope. The spectrum is characterised by a rising continuum due to warmdust, a silicate absorption and a strong [SIV] line at 10.5 micron. Weakerlines of [ArIII] at 9.0 micron and [NeII] at 12.8 micron are also present. Thecontinuum can be modeled by an optically thick emission from hot dust emissionextinguished by a cold foreground dust screen and a silicate absorption featurewith A_sil = 0.73+/-0.05 mag. We show how the spatial scale of the observationsgreatly determine the mid-IR appearance of NGC 5253 and the importantimplications that this has on the interpretation of line fluxes in terms of theproperties (age, IMF, etc.) of the embedded cluster. We have modeled theobserved line fluxes towards C2 using photoionisation models with the mostrecent spectral energy distributions available to describe the integratedproperties of the stellar cluster. Strong constraints on the geometry based onhigh spatial resolution observations at different wavelengths -- near-IR (HSTand Keck), mid-IR (TIMMI2) and radio (VLA) -- allows us to restrain theionisation parameters to values logU >= -0.5 dex. This constraint on U lead totwo possible solutions for the age and upper mass cutoff of C2: 1) a young (< 4Myr) cluster with a "non-standard" IMF with a low upper mass cutoff Mup < 50Msun, and 2) a cluster of ~5-6 Myr with a standard high upper mass cutoff (Mup\~ 100 Msun). Arguments in favour and against these two scenarios arepresented. The origin of the [OIV] 25.9 micron emission measured by ISO and thepossible presence of an intermediate mass black hole inside C2 are alsoaddressed.Comment: 19 pages, 5 tables and 5 figures. Accepted for publication in A&

High spatial resolution mid-infrared spectroscopy of NGC 5253: The stellar content of the embedded super-star cluster