  We report a new member of topological insulator (TI) family i.e.,
Mn$_2$Sb$_2$Te$_5$, which belongs to MnSb$_2$Te$_4$ family and is a sister
compound of Mn$_2$Bi$_2$Te$_5$. An antiferromagnetic layer of (MnTe)$_2$ has
been inserted between quintuple layers of Sb$_2$Te$_3$. The crystal structure
and chemical composition of as grown Mn$_2$Sb$_2$Te$_5$ crystal is
experimentally visualized by single crystal XRD (SCXRD) and field emission
scanning electron microscopy (FESEM). The valence states of individual
constituents i.e., Mn, Sb and Te are ascertained through X ray photo electron
spectroscopy (XPS). Different vibrational modes of Mn$_2$Sb$_2$Te$_5$ are
elucidated through Raman spectroscopy. Temperature-dependent resistivity of
Mn$_2$Sb$_2$Te$_5$ resulted in metallic behaviour of the same with an up-turn
at below around 20K. Further, the magneto-transport R(T) vs H of the same
exhibited negative magneto-resistance (MR) at low temperatures below 20K and
small positive at higher temperatures. The low Temperature -ve MR starts
decreasing at higher fields. The magnetic moment as a function of temperature
at 100Oe and 1kOe showed AFM like down turn cusps at around 20K and 10K. The
isothermal magnetization (MH) showed AFM like loops with some embedded FM/PM
domains at 5K and purely paramagnetic (PM) like at 100K. The studied
Mn$_2$Sb$_2$Te$_5$ clearly exhibited the characteristics of a magnetic TI
(MTI).
