The AuCu-type InPd3 (In0.5Pd1.5) (space group P4/mmm) has two independent positions (one Pd and randomly distributed between In and Pd). This phase was obtained as a major product when samples were rapidly quenched and it was supposed to be a metastable phase. Long annealing at around 750 K led to the two-fold ccp superstructure i.e. TiAl3 (space group I4/mmm) type with one In and two Pd positions which are orderly distributed in the structure. In fact, longer annealing at higher temperature led to fourfold ccp superstructure i.e. ZrAl3-type (space group I4/mmm) with one In and four perfectly ordered Pd positions (Table ). From these experimental findings, the thermodynamic stability order of these three polymorphs seems to be ZrAl3 type > TiAl3 type > AuCu type. This The ZrAl3 and TiAl3 structure types are the ordered variant of the fcc structure (AuCu3type). The In-In connectivity gradually breaks from 6 (AuCu3-type) to 5 (ZrAl3-type) to 4 (TiAl3-type) as shown in Fig. . Formation enthalpies (at zero K) of these three polymorphs of InPd3 were calculated and, it shows the order of ZrAl3-type > TiAl3-type > AuCu type (Fig. ). It is interesting to note that, the Madelung energies of these polymorphs also follow the same order. This energy order can be corroborated with the electronic density of states (DOS) (Fig. ). First of all, non-zero DOS across the Fermi level says about the metallic character of the different polymorphs of InPd3. For the ZrAl3-type structure, the Fermi level falls exactly at the pseudo-gap which is a clear indication of electronic and thermodynamic stability. The orbital-wise projected DOS shows a very distinct overlap between Pd -4d and In -5s/5p states; this leads to covalent-type In-Pd interactions propagating throughout the structure, lowering the number of free electrons in the system significantly, originates the state deficit region exactly at the Fermi level. A similar argument is also valid for the TiAl3-type structure, where the Fermi level falls very near to the state-deficient region (i.e. pseudo-gap), and it stands second in terms of stability between the three polymorphs of InPd3. The AuCu-type structure, where there is no such ordering between In and Pd positions and a high DOS across the Fermi level, indicates potential electronic instability.