In this study we report the results of study of novel ternary $Np_2PtGa_3$ compound. The x-ray-powder diffraction analysis reveals that the compound crystallizes in the orthorhombic CeCu$_2$-type crystal structure (space group Imma) with lattice para
meters $a$ = 0.4409(2) nm, $b$ = 0.7077(3) nm and $c$ = 0.7683(3) nm at room temperature. The measurements of dc magnetization, specific heat and electron transport properties in the temperature range 1.7 - 300 K and in magnetic fields up to 9 T imply that this intermetallic compound belongs to a class of ferromagnetic Kondo systems. The Curie temperature of $T_C sim$ 26 K is determined from the magnetization and specific heat data. An enhanced coefficient of the electronic specific heat of $gamma$ = 180 mJ/(mol at. Np K$^2$) and -lnT dependence of the electrical resistivity indicate the presence of Kondo effect, which can be described in terms of the S = 1 underscreened Kondo-lattice model. The estimated Kondo temperature $T_K sim$ 24 K, Hall mobility of $sim$ 16.8 cm$^2$/Vs and effective mass of $sim$ 83 $m_e$ are consistent with assumption that the heavy-fermion state develops in $Np_2PtGa_3$ at low temperatures. We compare the observed properties of $Np_2PtGa_3$ to that found in $Np_2PtGa_3$ and discuss their difference in regard to change in the exchange interaction between the conduction and localized 5f electrons. We have used the Fermi wave vector $k_F$ to evaluate the Rudermann-Kittel-Kasuya-Yosida (RKKY) exchange. Based on experimental data of the (U, Np)$_2$(Pd, Pt)Ga$_3$ compounds we suggest that the evolution of the magnetic ground states in these actinide compounds can be explained within the RKKY formalism.
Star-forming galaxies at redshifts z>6 are likely responsible for the reionization of the universe, and it is important to study the nature of these galaxies. We present three candidates for z~7 Lyman-break galaxies (LBGs) from a 155 arcmin^2 area in
the CANDELS/COSMOS field imaged by the deep FourStar Galaxy Evolution (zFourGE) survey. The FourStar medium-band filters provide the equivalent of R~10 spectroscopy, which cleanly distinguishes between z~7 LBGs and brown dwarf stars. The distinction between stars and galaxies based on an objects angular size can become unreliable even when using HST imaging; there exists at least one very compact z~7 candidate (FWHM~0.5-1 kpc) that is indistinguishable from a point source. The medium-band filters provide narrower redshift distributions compared with broad-band-derived redshifts. The UV luminosity function derived using the three z~7 candidates is consistent with previous studies, suggesting an evolution at the bright end (MUV -21.6 mag) from z~7 to z~5. Fitting the galaxies spectral energy distributions, we predict Lyman-alpha equivalent widths for the two brightest LBGs, and find that the presence of a Lyman-alpha line affects the medium-band flux thereby changing the constraints on stellar masses and UV spectral slopes. This illustrates the limitations of deriving LBG properties using only broad-band photometry. The derived specific star-formation rates for the bright LBGs are ~13 per Gyr, slightly higher than the lower-luminosity LBGs, implying that the star-formation rate increases with stellar mass for these galaxies.
The low-temperature specific heat of a superconductor Mo3Sb7 with T_c = 2.25 (0.05) K has been measured in magnetic fields up to 5 T. In the normal state, the electronic specific heat coefficient gamma_n, and the Debye temperature Theta_D are found t
o be 34.5(2) mJ/molK^2 and 283(5) K, respectively. The enhanced gamma_n value is interpreted due to a narrow Mo-4d band pinned at the Fermi level. The electronic specific heat in the superconducting state can be analyzed in terms a phenomenological two BCS-like gap model with the gap widths 2Delta_1/k_BT_c = 4.0 and 2Delta_2/k_BT_c = 2.5, and relative weights of the mole electronic heat coefficients gamma_1/gamma_n = 0.7 and gamma_2/gamma_n = 0.3. Some characteristic thermodynamic parameters for the studied superconductor, like the specific heat jump at T_c, DeltaC_p(T_c)/gamma_nT_c, the electron-phonon coupling constant,lambda_eph, the upper H_c2 and thermodynamic critical H_c0 fields, the penetration depth, lambda, coherence length xi, and the Ginzburg-Landau parameter kappa are evaluated. The estimated values of parameters like 2Delta/k_BT_c, DeltaC_p(T_c)/gamma_nT_c, N(E_F), and lambda_eph suggest that Mo3Sb7 belongs to intermediate-coupling regime. The electronic band structure calculations indicate that the density of states near the Fermi level is formed mainly by the Mo-4d orbitals and there is no overlapping between the Mo- 4d and Sb-sp orbitals.
