Investigation of the physical properties on an n- type GaP single crystal semiconductor compound is given. The magneto-optical properties, magneto photoconductivity, Hall effect as well as Seebeck and Nernst effects are measured for the same sample. A constructed basic experimental set-up for conducting these measurements is shown. An optical cryostat which is capable to control the sample temperature in the range of (200-340 K) is shown. The cryostat is also suitable for measuring electrical as well as thermal measurements. Results of energy gap is obtained from both optical absorption...