We have studied a compound (S)-(+)-4-(1-methylheptyl) 4-[4-(3-hexanoyloxyprop-1-oxy)benzoyloxy]biphenylate by means of differential scanning calorimeter, polarizing microscope and dielectric spectroscopy. This compound shows exceptionally a wide temperature range of SmC alpha* phase similar to 9 degrees C together with a paraelectric SmA* phase. A relaxation mechanism in the high kHz region has been detected for the SmC alpha* phase under planar orientation of the molecules. This mechanism has been characterized with temperature and bias electric field. Recent theoretical advances predict two different nature of dielectric relaxation mode in the SmC alpha* phase (Phys. Rev. E, 69, 031709, 2004). Our experimental results confirm two different behaviors of this relaxation mode in different temperature range of the phase.