Abstract: The invention relates to heat power engineering, in particular, to methods that use a working medium for producing useful work from heat of an external source. The method comprises interaction of the working medium with an energy source and interaction of the working medium with an additional low-temperature energy source in the form of the positron state of the Dirac's matter by means of bringing the working medium into quantum-mechanical resonance with said state. The quantum-mechanical resonance is initiated by changing at least one of the thermodynamic parameters of the working medium, while the value of spontaneous fluctuations of the variable parameter in the vicinity of the line of absolute instability in the state diagram of the working medium is predetermined, and the change step for the thermodynamic parameter is set to be lower than the predetermined value of said fluctuations.