Rare-earth orthochromites with distorted perovskite structure (e.g. Rcro 3 , R = Sm, Gd) have been under strong debate with respect to the origin of their ferroelectric order. of particular interest is the question of whether such orthochromites are, in fact, magnetically driven improper ferroelectrics, as many rare-earth manganites or orthoferrites. Here we show, by studying at the atomic scale the rareearth Smcro 3 system that a distortion of the Sm local environment emerges within the paramagnetic phase, near room temperature. Our Electric Field Gradient measurements combined with first-principles calculations show that the emergent phase cannot be simply ascribed to the Pna2 1 structure as reported for Gdcro 3 or Smcro 3. instead a local inhomogeneous state, where regular non-polar and polar distorted environments coexist, develops at low temperatures.

The development of new quantum materials involves both experimental and theoretical efforts to master the connection between the electronic structure and the desired macroscopic observables. This knowledge offers exceptional avenues to manipulate materials properties via symmetry, topology, and strong correlations [1]. Stoichiometric LaMnO 3 , a prototype strongly correlated electron system, exhibits an extremely delicate balance between lattice, spin and charge degrees of freedom, challenging still our understanding and offering many possibilities to create new states via external stimuli [2,3].According to the ligand field model, the 3d 4 valence orbitals of the Mn 3+ ions in LaMnO 3 , when in the octa hedral crystal field created by the nearestneighbour oxygen ions, are split into e g and t 2g irreducible representa tions, where the three fold t 2g states lie lower in energy than the twofold e g states due to the interaction among Mn and the O ligands. Additionally, the energy levels are filled according to Hund's rule, i.e. the Mn3d atomic states are in a t 3 2g e 1 g highspin configuration. The intraorbital exchange Hund's coupling provides an anisotropic occupation of the Mn3d related states, activating a cooperative Jahn-Teller (JT) distortion, responsible for a local symmetry lowering (distortion of the oxygen octahedra), and, consequently, lifting the orbital degeneracy by splitting both the e g and t 2g derived Mn3d states [4][5][6]. The fully activated JT distortion of the MnO 6 octa hedra stabilizes the Ctype orbital ordering [4, 7] and the system becomes orthorhombic, in the Pbnm crystal lographic group, with an insulating behaviour, presenting a magnetic phase transition from a paramagnetic to an Atype antiferromagnetic (AAFM) state, at 140 K [5, 8, 9].Ab initio calculations have been extensively applied to manganites, in particular for LaMnO 3 to predict its peculiar electronic, magnetic and structural ground state properties [6,7,[9][10][11][12][13][14][15][16].First principles modelling represents a powerful tool to investigate the properties of materials. However, there are still several methodological challenges that hinder an appropriate description of correlated electron systems. It is well certified in the literature that methods based on the density functional theory (DFT) in the framework of KohnSham scheme [17,18] generally fail in describing the interactions of the 3drelated energy levels.