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Planet-disc interactions build up local pressure maxima that may halt theradial drift of protoplanetary dust, and pile it up in rings and crescents.ALMA observations of the HD135344B disc revealed two rings in the thermalcontinuum stemming from ~mm-sized dust. At higher frequencies the inner ring isbrighter relative to the outer ring, which is also shaped as a crescent ratherthan a full ring. In near-IR scattered light images, the disc is modulated by a2-armed grand-design spiral originating inside the ALMA inner ring. Suchstructures may be induced by a massive companion evacuating the central cavity,and by a giant planet in the gap separating both rings, that channels theaccretion of small dust and gas through its filamentary wakes while stoppingthe larger dust from crossing the gap. Here we present ALMA observations in theJ=(2-1)CO isotopologue lines and in the adjacent continuum, with up to 12kmbaselines. Angular resolutions of 0.03" reveal the tentative detection of afilament connecting both rings, and which coincides with a local discontinuityin the pitch angle of the IR spiral, proposed previously as the location of theprotoplanet driving this spiral. Line diagnostics suggest that turbulence, orsuperposed velocity components, is particularly strong in the spirals. The12CO(2-1) 3-D rotation curve points at stellocentric accretion at radii withinthe inner dust ring, with a radial velocity of up to ~6%+-0.5% Keplerian, whichcorresponds to an excessively large accretion rate of ~2E-6M_sun/yr if all ofthe CO layer follows the 12CO(2-1) kinematics. This suggests that only thesurface layers of the disc are undergoing accretion, and that the linebroadening is due to superposed laminar flows.

A dusty filament and turbulent CO spirals in HD135344B-SAO206462