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Active pre-main-sequence binaries with separations of around ten stellarradii present a wealth of phenomena unobserved in common systems. The study ofthese objects is extended from Classical T Tauri stars to the Herbig Ae star HD104237. Spectro-interferometry with the VLTI/AMBER is presented.  It is found that the K-band continuum squared visibilities are compatiblewith a circumbinary disc with a radius of ~0.5 AU. However, a significantfraction (~50 per cent) of the flux is unresolved and not fully accounted bythe stellar photospheres. The stars probably don't hold circumstellar discs, inaddition to the circumbinary disk, due to the combined effects of innermagnetospheric truncation and outer tidal truncation. This unresolved fluxlikely arises in compact structures inside the tidally disrupted circumbinarydisc.  Most ($\gtrsim 90$ per cent) of the Br gamma line emission is unresolved. Theline-to-continuum spectro-astrometry shifts in time, along the direction of theLy alpha jet known to be driven by the system. The shift is anti-correlatedwith the Br gamma equivalent width. It is shown that the unresolved Br gammaemission cannot originate in the jet but instead is compatible with stellaremission from the orbiting binary components. The increase in the absolutevalue of the equivalent width of the line takes place at periastron passage; itcould arise in an accretion burst, a flare or in the increase in effective sizeof the emission region by the interaction of the magnetospheres. The binarylongitude of the ascending node is found to be $\Omega=(235\pm3)\degr$ and theorbit retrograde.  The origin of the jet is revisited. The tidal disruption of the circumstellardisks creates difficulties to ejection models that rely on stellarmagnetosphere and disc coupling. A scenario of a stellar wind collimated by acircumbinary disc wind is suggested.

Pre-main-sequence binaries with tidally disrupted discs: the Br gamma in HD 104237