title: Nontrivial Recurrent Intergrowth Structure and Unusual Magnetic Behavior of Intermetallic Compound Fe32+δGe33As2.
abstract: A new phase Fe32+δGe33As2(δ ≤ 0.136) was obtained by two-step synthesis from the elements. Fe32+δGe33As2crystallizes in its own structure type (space group P6/mmm, Z = 1, a = 11.919(3) Å, c = 7.558(4) Å) that can be described as a recurrent two-dimensional intergrowth of two intermetallic structure types, MgFe6Ge6and Co2Al5. Their blocks are represented by infinite columns in the structure. No visible structural changes were observed in the temperature range from 10 to 300 K. At 125 K, Fe32+δGe33As2undergoes an antiferromagnetic-like transition, while above 150 K it shows a typical Curie-Weiss paramagnetic behavior. Below the transition temperature, a peculiar field-dependent magnetic susceptibility, that shows a significant increase of the susceptibility upon increasing the magnetic field, and a change in transport properties have been observed. Above 140 K, Fe32+δGe33As2reveals a metallic behavior, in agreement with electronic structure calculation, while below this point the resistivity nonmonotonically increases upon cooling. The Seebeck coefficient is positive, indicating that holes are the major charge carriers, and shows a broad maximum around 57 K.
authors.affiliation: Department of Chemistry, Lomonosov Moscow State University , 119991 Moscow, Russia.
authors.forename: Roman A
authors.initials: RA
authors.lastname: Khalaniya
authors.affiliation: Department of Chemistry, Lomonosov Moscow State University , 119991 Moscow, Russia.
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Mironov
authors.affiliation: Department of Chemistry, Lomonosov Moscow State University , 119991 Moscow, Russia.|National Institute of Chemical Physics and Biophysics , 12618 Tallinn, Estonia.
authors.forename: Valeriy Yu
authors.identifier: http://orcid.org/0000-0002-8000-425X
authors.initials: VY
authors.lastname: Verchenko
authors.affiliation: Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , 86135 Augsburg, Germany.
authors.forename: Anton
authors.initials: A
authors.lastname: Jesche
authors.affiliation: Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg , 86135 Augsburg, Germany.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Tsirlin
authors.affiliation: Department of Chemistry, Lomonosov Moscow State University , 119991 Moscow, Russia.
authors.forename: Andrei V
authors.identifier: http://orcid.org/0000-0002-8316-3280
authors.initials: AV
authors.lastname: Shevelkov