Report .rdl with special characters & upload with power Shell

[Anonymous]

I have a report with some special characters, the special characters specifically are "à, è ".
When I run it or manually upload the report to the server I have no problem. But when I load the report with power shell with "Write-RsFolderContent" function I get an error.
In power shell console the error is
"Failed to create catalog item from 'C:\Users\rtn\Desktop\New folder\hprs\Shared Reports\Daily\Agent Activity.rdl' in '/Hash Phones Reporting Services DLL/Shared 
Reports/Daily': System.Exception: Failed to create catalog item C:\Users\rtn\Desktop\New folder\hprs\Shared Reports\Daily\Agent Activity.rdl : Eccezione durante la 
chiamata di "CreateCatalogItem" con "7" argomento/i: "System.Web.Services.Protocols.SoapException: The definition of this report is not valid or supported by this 
version of Reporting Services. The report definition may have been created with a later version of Reporting Services, or contain content that is not well-formed or not 
valid based on Reporting Services schemas. Details: Invalid character in the given encoding. Line 2399, position 44."

The enconding of report is UTF-8