diff --git a/matlab/read_field_complete_ucftar.m b/matlab/read_field_complete_ucftar.m
index 5c2fb9a..aa561cd 100644
--- a/matlab/read_field_complete_ucftar.m
+++ b/matlab/read_field_complete_ucftar.m
@@ -1,8 +1,8 @@
-function [q,x,y,z] = read_field_complete_ucftar(file,field,varargin)
+function [q,x,y,z] = read_field_complete_ucftar(htar,field,varargin)
     % [q,x,y,z] = read_field_complete_ucftar(file,field,varargin)
     % Reads a specific field from all processor chunks.(UCF tar version)
     % Input
-    %   file                name of tar-file to be read
+    %   htar                handle of tar file (ustar object)
     %   field               field to be read 
     %                         {'u','v','w','p','s1','s2',...}
     % ? step                index of step to be read (default: 1)
@@ -18,7 +18,7 @@ function [q,x,y,z] = read_field_complete_ucftar(file,field,varargin)
     addParamValue(par,'verbosity',0,@isnumeric);
     addParamValue(par,'debug',0,@isnumeric);
     parse(par,varargin{:});
-    istep = par.Results.timestep;
+    istep = par.Results.step;
 
     % Parse field
     switch field(1)
@@ -30,10 +30,6 @@ function [q,x,y,z] = read_field_complete_ucftar(file,field,varargin)
     otherwise; error('Invalid field: %s',field);
     end
     
-    % Open tar file
-    htar = ustar();
-    htar.open(file);
-    
     % Read parameters
     params = read_parameters_ucf(htar,'tarmode',1);
     
@@ -57,7 +53,4 @@ function [q,x,y,z] = read_field_complete_ucftar(file,field,varargin)
       [data,ib,jb,kb,nxl,nyl,nzl] = read_field_chunk_ucf(htar,field,'tarmode',1,'rank',iproc,'ghost',0,'step',istep);
       q(ib:ib+nxl-1,jb:jb+nyl-1,kb:kb+nzl-1) = data;
     end
-    
-    % Close tar file
-    htar.close();
 end