NdBa(2)Cu(3)O(7-delta)thin film deposited on a MgO substrate has been verified to remain solid above its peritectic melting temperature (T-p). Such a superheating nature is attributed to its low energy surface and epitaxial interface with substrate. Here, combining superheating nature with doping effect, we report a novel structure, Mg-doped NdBa(2)Cu(3)O(7-delta)film with YBa(2)Cu(3)O(7-delta)buffer layer for the first time. Remarkably, this film presents a higher thermal stability level than heretofore possible when acting as a seed for preparing SmBa(2)Cu(3)O(7-delta)bulks by melt growth, enduring a temperature of 1128 degrees C, 43 K above itsT(p)for 1 hour. The utilization of such a highT(max)in melt growth is beneficial to the fabrication of large-sized and high-performance bulk in terms of effectively broadening the growth window and suppressing the heterogeneous nucleation. More importantly, some high thermal stability required technological applications, such as batch growth and failed bulk recycling, are likely to be realized by this novel Mg-doped NdBa(2)Cu(3)O(7-delta)film seed. Finally, we show how the observed metastable phase is linked to the distinctive film architecture.