A heat exchanger, in particular for an exhaust system of an internal combustion engine, preferentially in a motor vehicle, - with at least one thermoelectric generator, which comprises multiple thermoelectric elements, each of which have a hot side and a cold side, - with at least one heating channel for conducting a heating medium, which is arranged on the hot sides of the thermoelectric elements of at least one such thermoelectric generator, - with at least one cooling channel for conducting a cooling medium, which is arranged on the cold sides of the thermoelectric elements of at least one such thermoelectric generator, - wherein the at least one thermoelectric generator, the at least one heating channel and the at least one cooling channel are arranged adjacent in a stacking direction and form a channel stack, - with a housing, which covers an interior space receiving the channel stack, which comprises a cooling medium inlet, a cooling medium outlet, a heating medium inlet and a heating medium outlet as well as electrical connections for the respective thermoelectric generator, - wherein in the interior space of the housing at least one double-walled intermediate bottom is arranged, in which the thermoelectric elements of such a thermoelectric generator are arranged and which fluidically separates such a cooling channel from such a heating channel which is adjacent thereto, characterized - in that at least two such heating channels are fluidically connected to one another via heating medium connecting tubes, which extend through a cooling channel and through at least one intermediate bottom, wherein the heating medium connecting tubes extend spaced from the housing in the interior space and are exposed to the cooling medium within the respective cooling channel, and/or - in that at least two such cooling medium channels are fluidically connected to one another via cooling medium connecting tubes, which extend through a heating channel and through at least one intermediate bottom, wherein the cooling medium connecting tubes extend spaced from the housing in the interior space and are exposed to the heating medium within the respective heating channel. - with at least one thermoelectric generator, which comprises multiple thermoelectric elements, each of which have a hot side and a cold side, - with at least one heating channel for conducting a heating medium, which is arranged on the hot sides of the thermoelectric elements of at least one such thermoelectric generator, - with at least one cooling channel for conducting a cooling medium, which is arranged on the cold sides of the thermoelectric elements of at least one such thermoelectric generator, - wherein the at least one thermoelectric generator, the at least one heating channel and the at least one cooling channel are arranged adjacent in a stacking direction and form a channel stack, - with a housing, which covers an interior space receiving the channel stack, which comprises a cooling medium inlet, a cooling medium outlet, a heating medium inlet and a heating medium outlet as well as electrical connections for the respective thermoelectric generator, - wherein in the interior space of the housing at least one double-walled intermediate bottom is arranged, in which the thermoelectric elements of such a thermoelectric generator are arranged and which fluidically separates such a cooling channel from such a heating channel which is adjacent thereto, - in that at least two such heating channels are fluidically connected to one another via heating medium connecting tubes, which extend through a cooling channel and through at least one intermediate bottom, wherein the heating medium connecting tubes extend spaced from the housing in the interior space and are exposed to the cooling medium within the respective cooling channel, and/or - in that at least two such cooling medium channels are fluidically connected to one another via cooling medium connecting tubes, which extend through a heating channel and through at least one intermediate bottom, wherein the cooling medium connecting tubes extend spaced from the housing in the interior space and are exposed to the heating medium within the respective heating channel.