Quaternary Germanides RE₄Mn₂InGe₄ (RE = La–Nd, Sm, Gd–Tm, Lu)

The quaternary germanides RE₄Mn₂InGe₄ (RE = La–Nd, Sm, Gd–Tm, Lu) have been prepared by arc-melting reactions of the elements and annealing at 800 °C and represent the second example of the RE₄M₂InGe₄ series previously known only for M = Ni. Single-crystal X-ray diffraction studies conducted on the earlier RE members of RE₄Mn₂InGe₄ confirmed that they adopt the monoclinic Ho₄Ni₂InGe₄-type structure [space group <i>C</i>2/<i>m</i>, <i>a</i> = 16.646(2)–15.9808(9) Å, <i>b</i> = 4.4190(6)–4.2363(2) Å, <i>c</i> = 7.4834(10)–7.1590(4) Å, β = 106.893(2)–106.304(1)° in the progression of RE from La to Gd]. The covalent framework contains Mn-centered tetrahedra and Ge₂ dimers that build up [Mn₂Ge₄] layers, which are held weakly together by four-coordinate In atoms and outline tunnels filled by the RE atoms. This bonding picture is supported by band-structure calculations. An alternative description based on Ge-centered trigonal prisms reveals that RE₄Mn₂InGe₄ is closely related to RE₂InGe₂. The electrical resistivity behavior of Pr₄Mn₂InGe₄ is similar to that of Pr₂InGe<sub>2