An external nozzle member for a turbomachine longitudinally extending along an axis oriented from upstream to downstream, said turbomachine comprising at least one primary stream configured to conduct a primary flow from upstream to downstream and at least one annular cavity of axis in which a cooling air flow (Fr) circulates, said turbomachine comprising at least one turbine casing mounted along the axis upstream of the external nozzle member and comprising at least one turbine casing flange extending downstream of the turbine casing, said external nozzle member being configured so as to radially externally delimit the primary stream with respect to the axis at the outlet of the turbomachine, said external nozzle member comprising - at least one acoustic attenuation structure comprising an internal face and an external face, - at least one internal wall mounted to the internal face of the acoustic attenuation structure and facing the primary stream and - at least one external wall mounted to the external face of the acoustic attenuation structure and facing the annular cavity, said acoustic attenuation structure, said internal wall and said external wall forming an acoustic attenuation panel, - at least one nozzle flange connected to the acoustic attenuation panel and comprising at least one upstream end configured to be connected to the turbine casing flange and - at least one sealing member connected to the acoustic attenuation panel and comprising at least one internal longitudinal branch with respect to the axis, - the external nozzle member being characterized in that the internal longitudinal branch of the sealing member radially internally extends to the nozzle flange with respect to the axis, so as to thermally protect said nozzle flange from the primary flow, the nozzle flange being made of a first material and the sealing member being made of a second material, the first material having a higher coefficient of thermal expansion than the second material. - at least one acoustic attenuation structure comprising an internal face and an external face, - at least one internal wall mounted to the internal face of the acoustic attenuation structure and facing the primary stream and - at least one external wall mounted to the external face of the acoustic attenuation structure and facing the annular cavity, said acoustic attenuation structure, said internal wall and said external wall forming an acoustic attenuation panel, - at least one nozzle flange connected to the acoustic attenuation panel and comprising at least one upstream end configured to be connected to the turbine casing flange and - at least one sealing member connected to the acoustic attenuation panel and comprising at least one internal longitudinal branch with respect to the axis, - the external nozzle member being characterized in that the internal longitudinal branch of the sealing member radially internally extends to the nozzle flange with respect to the axis, so as to thermally protect said nozzle flange from the primary flow, the nozzle flange being made of a first material and the sealing member being made of a second material, the first material having a higher coefficient of thermal expansion than the second material.