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tion (XRD) spectra were taken with Cu K$_{α}$ radiation ( λ =1 . 5418 ˚ A) using a Rigaku Miniflex X-ray machine. X-ray diffraction (XRD) results of the ground samples indicate the phases for both of them are pure. The lattice parameters, a=b=3.798(2) ˚ A, c=6.063(2) ˚ A and a=b=3.818(2) ˚ A, c=6.243(2) ˚ A for nominal composition FeTe$_{0}$$_{.}$$_{5}$Se$_{0}$$_{.}$$_{5}$ and FeTe$_{0}$$_{.}$$_{9}$Se$_{0}$$_{.}$$_{1}$, respectively, are obtained by fitting the XRD spectra using the Rietica software. 26 On the other hand, X-ray diffraction (XRD) spectra of single crystals reveal that the crystal surface is normal to the c-axis with the plate-shaped surface parallel to the ab-plane. The elemental and microstructure anal- ysis were performed using energy-dispersive x-ray spec- troscopy in an JEOL JSM-6500 scanning electron mi- croscope. The average stoichiometry was determined by examination of multiple points on the crystals. The measured compositions are Fe$_{1}$$_{.}$$_{02(3)}$Te$_{0}$$_{.}$$_{61(4)}$Se$_{0}$$_{.}$$_{39(4)}$ and Fe$_{1}$$_{.}$$_{05(3)}$Te$_{0}$$_{.}$$_{89(2)}$Se$_{0}$$_{.}$$_{11(2)}$. They will be denoted as Se-39 and Se-11 in the following for brevity. Electrical trans- port measurements were performed using a four-probe configuration on rectangular shaped polished single crys- tals with current flowing in ab-plane of tetragonal struc- ture. Thin Pt wires were attached to electrical contacts made of Epotek H20E silver epoxy. Sample dimensions were measured with an optical microscope Nikon SMZ- 800 with 10 µ m resolution. Electrical transport measure- ments were carried out in dc fields up to 9T in a Quantum Design PPMS-9 from 1.8 to 200 K and up to 35 T in a resistive magnet in a He3 cryostat down to 0.3 K at the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, FL. 

Temperature dependent resistivity of ρ$_{ab}$ ( T ) of Se-39 and Se-11 below 15 K in low magnetic fields from 0 to 9 T for H ‖ ab and H ‖ c are shown in Fig. 1. With in- creasing magnetic fields, the resistivity transition width becomes slightly broader and the onset of superconduc- tivity gradually shifts to lower temperatures. The trend is more pronounced for H ‖ c than H ‖ ab. This is similar to previous reports for Fe(Te,S) and FeTe$_{0}$$_{.}$$_{7}$Se$_{0}$$_{.}$$_{3}$ single crystals. 27 , 28 It is worth noting that the shape and width of ρ$_{ab}$ ( T ) broadening with H ‖ c is comparable to that of the 122-system, e.g. the single crystal of (Ba,K)Fe$_{2}$As$_{2}$ and (Ba,Rb)Fe$_{2}$As$_{2}$. 29 , 30 It is rather different from 1111- system such as single crystal of SmO$_{0}$$_{.}$$_{7}$F$_{0}$$_{.}$$_{25}$FeAs and SmO$_{0}$$_{.}$$_{85}$FeAs. 19 , 31 Similar field broadening of resistiv- ity of the 1111-system with H ‖ c was also observed in cuprates. 32 − 34 and explained by the vortex-liquid state. 35 Recent report on NdFeAsO$_{1}$$_{−}$$_{x}$F$_{x}$ single crys- tals confirmed the existence of the vortex-liquid state in 1111-system. 36 Hence, the vortex-liquid state region is narrower even absent in Fe(Te,Se) (11-system). 

Insets of Fig. 1(a) and (c) show the temperature de- pendence of the resistivity ρ$_{ab}$ ( T ) for Se-39 and Se-11 at zero field from 1.8K to 200 K. Both undergo a relatively 

## III. RESULTS 

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sharp superconducting transition at T$_{c,onset}$ =14.4 K and 12 K for Se-39 and Se-11, respectively. It should be noted that, as seen from the insets, Se-39 exhibits a metallic re- sistivity behavior in normal state, whereas Se-11 is not metallic. This difference can be ascribed to different Se content. 12 , 37 The non-metallic behavior of Se-11 has also been observed in low S doped FeTe single crystals. 27 In addition, more excess Fe in Fe(2) site for Se-11 than Se- 39 could lead to weak charge carrier localization. 28 , 38 On the other hand, there is an anomalous peak in ρ$_{ab}$ ( T ) for Se-11 at T ≃ 42K. It corresponds to simultaneous struc- tural and (or) antiferromagnetic transitions. Comparing with undoped FeTe, 39 the transtion has been depressed from around 65K to 42K. 

Fig. 2 shows the upper critical field µ$_{0}$H$_{c}$$_{2}$ ( T ) of Se- 39 and Se-11 corresponding to the temperatures where the resistivity drops to 90% of the normal state resis- tivity ρ$_{n,ab}$ ( T, H )( T$_{c,onset}$ ), 50% of ρ$_{n,ab}$ ( T, H )( T$_{c,middle}$ ) 

