Calorimetric study of the giant magnetocaloric effect in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mi>MnNiSi</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>0.56</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mi>FeNiGe</mml:mi><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>0.44</mml:mn></mml:mrow></mml:msub></mml:math>

${(\mathrm{MnNiSi})}_{0.56}{(\mathrm{FeNiGe})}_{0.44}$ belongs to a new family of alloys, similar MnAs, showing magnetostructural first-order transition near room temperature with large latent heat and magnetocaloric effect (MCE). From isothermal magnetization, remarkable values the entropy change have been reported, such as $|\mathrm{\ensuremath{\Delta}}{S}_{T}|=11.5$ J/kg K at 290 for small field 1 T, or $|\mathrm{\ensuremath{\Delta}}{S}_{T}|=70.1$ 5 T on slightly different composition. Strangely, this last value almost doubles that obtained from Clausius-Clapeyron equation. Therefore, very detailed set calorimetric determinations made including capacity by adiabatic differential scanning calorimetry (DSC), direct measurement absorbed demagnetization several magnetothermal histories sample. We found high $|\mathrm{\ensuremath{\Delta}}{S}_{T}|=45.7$ 289.4 7 sample previously cooled low then heated under magnetic target temperature. This is but far reported data, which happened be nonphysical frequently used, incorrect, experimental protocol determine $\mathrm{\ensuremath{\Delta}}{S}_{T}$ via Maxwell relation. The spurious contribution has analyzed computed, explaining values. strong thermal hysteresis 8.4 8.3 respectively, make alloy useless refrigeration, results encourage searching other derivatives lower could even higher $|\mathrm{\ensuremath{\Delta}}{S}_{T}|$.